Why Is There a Bump Under My Nail? Causes and Concerns

A bump under your nail can be anything from a harmless wart to a rare tumor, and the wide range of possibilities is exactly why these lumps deserve attention rather than dismissal. Most subungual bumps (the medical term for growths beneath the nail plate) turn out to be benign, but because all of them tend to cause the same vague symptoms like nail lifting, ridging, or discoloration, even doctors sometimes struggle to tell them apart without further investigation. Understanding the most likely culprits, and the red flags that separate the routine from the worrisome, can help you decide how urgently to seek care.

Warts, Cysts, and Bone Spurs: The Most Common Culprits

If you have a firm bump under or around your nail that appeared gradually, one of the three most statistically likely explanations is a subungual or periungual wart, a mucous cyst, or a bony outgrowth called a subungual exostosis. Each has a fairly distinctive profile once you know what to look for.

Subungual warts are caused by the human papillomavirus (HPV) and tend to show up as rough, slightly raised areas beneath or beside the nail. They can distort the nail plate, cause pain when you press on them, and be stubbornly resistant to over-the-counter treatments because the nail itself shields the virus from topical remedies.¹ Warts are far more common in children and young adults, and while they can resolve on their own over months to years, many people seek treatment because of discomfort or cosmetic frustration.

Mucous cysts, also called myxoid cysts, are small fluid-filled sacs that typically develop near the last joint of a finger. They are strongly associated with osteoarthritis and tend to appear in middle-aged and older adults.² When a mucous cyst presses against the nail matrix (the tissue responsible for growing the nail), it creates a groove or ridge that runs lengthwise down the nail. The bump itself is often translucent and slightly squishy. Some people are tempted to pop them, but puncturing a mucous cyst at home raises the risk of joint infection, so this is one you want a doctor to handle.

Subungual exostosis is a bony growth that sprouts from the tip of the finger or toe bone beneath the nail. It is most common on the big toe and tends to push the nail upward, sometimes making it look like an ingrown nail that will not heal. On an X-ray, you can see the growth extending from the bone with a continuous connection to it, which helps confirm the diagnosis.³ Because this is essentially an overgrowth of normal bone and cartilage, it is benign, but it often needs surgical removal if it is causing pain or nail deformity.

Glomus Tumors and the Mystery of Disproportionate Pain

Among the less common but highly distinctive causes of a subungual bump is the glomus tumor, a tiny growth arising from the glomus body, a specialized structure in your fingertips that helps regulate blood flow and temperature. What makes glomus tumors remarkable is the sheer amount of pain they produce relative to their size. Many are only a few millimeters across, yet they can cause years of severe, shooting pain that seems wildly out of proportion to what you see on the surface.

The classic triad of symptoms is localized tenderness at a specific point under the nail, pain that flares with cold exposure, and intense pain triggered by even minor bumps or pressure.⁴ If you can pinpoint a single spot under your nail where even light touch with a pen tip produces sharp pain, that is a strong clue. Cold sensitivity is another hallmark: people with glomus tumors often describe agony when reaching into a freezer or holding a cold drink.⁵

Despite this distinctive presentation, glomus tumors are frequently misdiagnosed for years because they are small enough to hide from casual examination, and many clinicians simply do not think of them. In some cases, there is no visible swelling at all, just relentless fingertip pain.⁶ MRI is the preferred imaging tool for localizing these tumors before surgery, because it can detect the small, well-defined lesion even when it is invisible to the naked eye.⁷ Once found, surgical excision resolves the pain reliably, and modern approaches can often spare the nail itself, avoiding permanent nail deformity.⁸

Less Common Benign Growths

A few other benign lesions can present as a bump or irregularity under the nail. They are rarer than warts or cysts, but worth knowing about because they can mimic more serious conditions.

Onychopapilloma is a benign growth of the nail bed that typically shows up as a single red or reddish streak running down the length of the nail, sometimes accompanied by a thickened area of skin (subungual keratosis) where the nail meets the fingertip. The nail plate over the growth often lifts slightly in that one spot.⁹ It is painless and generally harmless, though it can be confused with more concerning causes of nail streaks, which makes a biopsy worthwhile if the appearance is ambiguous.

Periungual fibromas, sometimes called Koenen tumors, are firm, flesh-colored growths that emerge from beneath or beside the nail fold. They are closely linked to a genetic condition called tuberous sclerosis complex, and their presence is often what prompts doctors to investigate for that broader diagnosis.¹⁰ If you develop multiple periungual fibromas, particularly on several fingers or toes, your doctor will likely want to check for other signs of tuberous sclerosis such as skin patches or kidney issues. A single isolated fibroma, while less concerning, still merits evaluation.

Nail Psoriasis and Other Inflammatory Causes

Not every bump or irregularity under the nail is a growth in the traditional sense. Inflammatory skin conditions, especially psoriasis, can produce changes beneath the nail plate that feel bumpy or raised and look abnormal on close inspection.

When psoriasis affects the nail bed, it can cause salmon-colored spots (sometimes called oil-drop spots), a buildup of scaly skin under the nail (subungual hyperkeratosis), and tiny splinter-like hemorrhages running lengthwise under the nail plate.¹¹ The subungual hyperkeratosis can create a chalky, raised area beneath the nail that you might describe as a bump, and it can lift the nail away from the bed. If you already have psoriasis elsewhere on your body, nail involvement is quite common. But some people develop nail psoriasis without obvious skin plaques, which makes the nail changes harder to connect to the underlying condition.

Other inflammatory conditions like lichen planus and eczema can also alter the nail bed and surrounding structures, though they more often produce thinning, ridging, or brittleness rather than a discrete bump. Fungal nail infections (onychomycosis) deserve a mention here too: a thick, crumbly buildup of debris under the nail from a chronic fungal infection can sometimes feel like a lump, though it is usually more diffuse and accompanied by yellow-brown discoloration.

When a Bump Under the Nail Could Be Cancer

This is the section people are really worried about, and the honest answer is that malignant tumors under the nail are uncommon but real, and they are frequently diagnosed late because they look so much like benign problems. Two cancers account for the vast majority of subungual malignancies: melanoma and squamous cell carcinoma.

Subungual melanoma often starts as a dark streak running along the nail, usually brown or black, that gradually widens over months to years. A key warning sign is the Hutchinson sign, where the dark pigment extends beyond the nail onto the surrounding skin fold.¹² But subungual melanoma does not always look like the textbook description. It can present as a non-pigmented bump, a chronic nail-bed sore that will not heal, or what appears to be a traumatic injury. In one reported case, a patient’s subungual melanoma was initially treated as a chronic traumatic nail-bed injury for over a year before the correct diagnosis was made, by which point the cancer had already spread to the lymph nodes.¹³ That kind of delayed diagnosis is disturbingly common with nail melanoma, in part because patients and doctors alike tend to attribute nail changes to injury or infection before considering cancer.

Squamous cell carcinoma (SCC) of the nail unit is sometimes called the “great mimicker” because it can look like a wart, a fungal infection, a chronic paronychia (nail fold infection), or even an ingrown nail.¹⁴ It typically grows slowly and is often linked to HPV infection, particularly on the fingers. Like melanoma, there is frequently a long gap between when symptoms first appear and when someone gets a definitive diagnosis, precisely because the early presentation is so non-specific. The takeaway is not to panic about every nail change, but to pay attention when a nail abnormality does not improve with standard treatment, or when it affects only a single nail with no clear cause.

Red Flags Worth Acting On

Given that benign and malignant conditions under the nail can look so similar, knowing which features should prompt a faster trip to the doctor is genuinely useful. Delays in diagnosing subungual tumors are common specifically because so many different conditions produce the same nonspecific nail deformity.¹⁵

Features that raise concern include:

A dark streak: A new or widening band of brown or black pigment running lengthwise along the nail, especially if it bleeds into the surrounding skin (the Hutchinson sign).
Single-nail involvement: When only one nail is affected and there is no history of injury, infection, or systemic skin disease, the chance that something more significant is happening goes up.
Non-healing lesions: A sore, lump, or area of bleeding under the nail that persists for more than a few weeks despite treatment.
Rapid growth: Any subungual mass that noticeably enlarges over weeks to months.
Nail destruction: Progressive splitting, crumbling, or loss of the nail plate in a single digit without an obvious mechanical explanation.

None of these features automatically means cancer. A dark streak is very common in people with darker skin tones, where it is usually benign melanocyte activation. And plenty of single-nail problems turn out to be warts or cysts. But any of these features persisting without improvement warrants a dermatology or hand surgery referral.

How Doctors Figure Out What the Bump Is

Because so many subungual conditions look alike from the outside, doctors often need more than a visual exam to reach a diagnosis. The workup typically escalates from non-invasive to invasive depending on what the initial assessment suggests.

Dermoscopy, where a dermatologist examines the nail with a magnifying device and polarized light, is usually the first step. This can reveal patterns in pigmentation, blood vessel structure, and surface texture that help narrow the possibilities. For lesions suspected to involve bone, a plain X-ray is fast and inexpensive: it can immediately show a subungual exostosis or an enchondroma (a cartilage tumor within the bone) and rule out bony destruction from a malignancy.

When soft-tissue detail matters, MRI is the imaging method of choice. It is particularly useful for localizing glomus tumors before surgery, because the tumor’s size and exact position under the nail determine which surgical approach will preserve the nail best.⁷ Contrast-enhanced CT is a reasonable second option when MRI is unavailable or contraindicated.

Biopsy remains the definitive way to tell benign from malignant. For nail-bed lesions, this usually involves partially or fully removing the nail plate to access the tissue underneath, which understandably makes patients hesitant. But when the clinical picture is unclear, particularly if there is any suspicion of melanoma or SCC, a biopsy is not something to delay. The consequences of catching a malignancy months earlier versus later can be significant.

Treatment Depends Entirely on the Cause

There is no single treatment for “a bump under the nail” because the causes span such a wide range. What works depends on what the bump actually is.

Warts can be treated with cryotherapy, laser therapy, or injected medications like bleomycin, though subungual warts are notoriously harder to clear than warts in other locations because the nail plate acts as a physical barrier.¹ Mucous cysts frequently recur after simple drainage, so definitive treatment often involves surgically removing the cyst along with the underlying bone spur (osteophyte) at the joint, which addresses the root cause.² Subungual exostoses are removed surgically by shaving or excising the bony growth, and they rarely come back after complete excision.

Glomus tumors are treated with surgical excision, and modern nail-sparing techniques allow surgeons to remove the tumor through a small window in the nail bed without taking off the entire nail plate. In studies using this approach, patients showed no recurrence of symptoms and maintained normal nail appearance during follow-up.⁸ For people who have endured years of unexplained fingertip pain, the relief after surgery is often dramatic and immediate.

For nail psoriasis, treatment focuses on managing the underlying inflammatory process rather than removing tissue. Topical steroids, vitamin D analogs, and in severe cases, systemic medications like biologics can improve the nail bed changes over time, though nail psoriasis tends to respond more slowly than skin psoriasis.

Malignant subungual tumors require more aggressive treatment. Subungual melanoma typically involves wide excision of the nail unit down to bone, and in advanced cases, amputation of the fingertip may be necessary. Squamous cell carcinoma of the nail unit is often curable with surgery when caught early, but delays in diagnosis sometimes mean the cancer has invaded deeper structures by the time it is identified.

Bumps Under Children’s Nails

Subungual bumps in children tend to have a different mix of causes than in adults. Pediatric nail disorders can be especially tricky to evaluate because children’s nails are thinner and grow faster, and kids are less able to describe their symptoms precisely.¹⁶

Warts are among the most common subungual growths in children, reflecting kids’ frequent skin-to-skin contact and the ubiquity of HPV in environments like swimming pools and playgrounds. Subungual exostoses, while less common than in adults, do occur in adolescents, particularly on the big toe after repetitive sports-related microtrauma. Congenital nail anomalies can also create bumps or irregularities that are present from birth or early childhood, including malalignment of the great toenail, where the nail plate grows at an angle to the nail bed and can create a ridge or raised area.

Malignant subungual tumors are exceedingly rare in children, but not unheard of. Pediatricians generally take a watch-and-wait approach for nail bumps that are not painful or rapidly changing, but any growth that persists, enlarges, or causes significant nail distortion should be evaluated by a specialist. The same red-flag principles from adults apply to children: a single nail affected without explanation, dark streaking, and non-healing lesions all warrant closer attention.

Why These Bumps Get Misdiagnosed So Often

One of the most consistent themes across the medical literature on subungual lesions is that they get misdiagnosed, or at least diagnosed late. The reasons are structural, not just a matter of individual doctor error.

For one thing, the nail itself is in the way. Unlike a skin lesion that a doctor can examine directly and biopsy easily, a subungual growth is hidden beneath a hard plate. Visual inspection is limited to what shows through the nail or at its edges. For another, many nail conditions share the same visible endpoints: lifting of the nail plate, ridging, thickening, discoloration. A wart, a glomus tumor, an SCC, and nail psoriasis can all produce a nail that looks roughly the same to the untrained eye. Research on subungual tumors has emphasized that both benign and malignant growths often follow what amounts to a shared pathway of nonspecific nail deformity, which makes clinical suspicion for malignancy especially important.¹⁵

Squamous cell carcinoma of the nail unit is a particularly vivid example. Its ability to mimic warts, fungal infections, and inflammatory conditions has earned it the label “the great mimicker,” and the average time from symptom onset to diagnosis can stretch across years.¹⁴ Similarly, glomus tumors are often misdiagnosed as neuromas, arthritis, or even psychological pain for years before someone finally orders an MRI. The practical lesson for patients is straightforward: if you have had a bump, pain, or nail change for months and no one has given you a confident answer, ask specifically about the possibility of a subungual tumor and whether imaging or biopsy is warranted. Persistence is not paranoia here; it is how these diagnoses eventually get made.

1
PubMed. Complete resolution of recalcitrant periungual/subungual wart with recovery of normal nail following “prick” method of administration of bleomycin 1%
2
Frontiers in Surgery. Treatment of Mucous Cyst of the Distal Interphalangeal Joint With Osteophyte Excision and Joint Debridement
3
Foot & Ankle Surgery: Techniques, Reports & Cases. Subungual exostosis and chronic onychocryptosis: An intricate relationship – clinical review and management
4
PubMed Central. The hidden cause of chronic finger pain: Glomus Tumor – A Case Report
5
Radiology Case Reports. Glomus tumor: A rare differential diagnosis for subungual lesions
6
PubMed Central. The Tiny Tumor with Disproportionate Pain: Subungual Glomus Tumor of the Thumb Managed with Nail-Sparing Excision: A Case Report
7
PubMed Central. Radiological Imaging of Nail Disorders (PART II) – Radiological Features of Nail Disease – Section: Tumors and Pseudo Tumors
8
PubMed Central. Excision of Subungual Glomus Tumor by Subungual Approach: A Useful Yet Underutilized Technique
9
PubMed. Longitudinal erythronychia with distal subungual keratosis: onychopapilloma of the nail bed and Bowen’s disease
10
PubMed Central. Multiple koenen tumors: an uncommon presentation
11
PubMed Central. Nail psoriasis: clinical features, pathogenesis, differential diagnoses, and management
12
PubMed. Hutchinson Sign: Biopsy May Assist in Diagnosis of Subungual Melanoma in Situ
13
PubMed Central. Missed opportunity to diagnose subungual melanoma: potential pitfalls!
14
PubMed Central. Squamous cell carcinoma of the nail unit
15
The Journal of Hand Surgery. Subungual Tumors: An Algorithmic Approach
16
PubMed Central. Pediatric Nail Disorders