Pain under the fingernail when pressed signals an issue within the confined space of the fingertip. The nail unit contains nerves, blood vessels, and specialized tissue, and any mass or fluid accumulation quickly translates into tenderness under the hard nail plate. This sensitivity can range from the discomfort of a simple bruise to the sharp reaction caused by a structural abnormality. Determining the cause depends on whether the pain started suddenly after an injury or has progressed slowly over time.
Common Causes Related to Injury and Inflammation
The most common reason for immediate pain upon pressing the fingernail is a subungual hematoma, a collection of blood trapped between the nail plate and the nail bed following trauma. A direct blow, such as slamming a finger in a door, ruptures small blood vessels underneath the nail. The rigid nail plate prevents the blood from escaping, and the resulting pressure buildup causes characteristic throbbing pain that worsens with any touch or pressure.
Infections around the nail unit, known as paronychia, are a frequent source of pressure-sensitive pain. This condition affects the nail fold, the skin surrounding the nail, allowing bacteria or fungi to enter through small cuts or breaks in the skin. The infection causes swelling, redness, and pus formation, and the inflamed tissue becomes acutely tender to any pressure applied to the area. Acute paronychia, often caused by bacteria like Staphylococcus, typically develops quickly and presents with warmth and throbbing discomfort.
A less obvious cause is repetitive microtrauma, where small, repeated stresses accumulate over time to irritate the nail bed or surrounding structures. Activities involving frequent tapping or pressure on the fingertips, such as playing certain musical instruments or high-volume typing, can lead to chronic irritation. This repeated stress may not cause a single dramatic injury but can result in chronic inflammation or subtle damage that makes the area tender to firm pressure. This constant, low-level irritation can also predispose the area to other issues.
Conditions That Cause Hypersensitivity to Pressure
When pain is disproportionately severe, highly localized, and not easily explained by a bruise or infection, structural growths underneath the nail may be the cause. The most well-known of these is the glomus tumor, a rare, benign growth arising from specialized glomus bodies found in the fingertip. These tumors are tiny, yet they produce excruciating, pinpoint pain that is highly sensitive to touch and cold temperatures.
The pain from a glomus tumor is classically described as sharp and paroxysmal, meaning it comes in sudden, intense bursts, and is immediately reproduced by applying pressure directly over the lesion. This extreme sensitivity to pressure, along with a marked intolerance to cold water, helps distinguish it from other causes of fingertip pain. The tumor’s mass effect within the confined space under the nail, coupled with its highly innervated nature, accounts for the severe reaction to minimal external force.
Other structural issues also cause pressure sensitivity, including subungual exostosis and epidermoid cysts. A subungual exostosis is a benign bony spur that grows outward from the bone of the fingertip underneath the nail bed. As this hard growth expands, it pushes upward, deforming the nail and causing pain when pressure is applied to the nail plate, compressing the sensitive tissue against the bone.
Subungual epidermoid cysts are noncancerous sacs filled with keratin. These cysts can form after a minor injury traps skin cells beneath the nail bed, where they continue to multiply and fill with debris. As the cyst slowly enlarges, the increasing internal pressure causes localized tenderness and pain when the area is pressed. Their location under the rigid nail forces them to exert pressure on the surrounding nerves and tissue.
When to Consult a Healthcare Professional
Seek medical attention if the pain under the fingernail is severe, persistent, or accompanied by specific warning signs. Immediate care is warranted for rapidly worsening pain, uncontrolled throbbing, or signs of a spreading infection. These signs include redness or warmth extending beyond the nail area, the presence of pus, or the onset of fever.
If the pain is not severe but lasts for more than two weeks without improvement, a medical consultation is advisable. This is particularly true if the pain is recurrent, or if you notice a persistent, unexplained discoloration or a lump beneath the nail that does not grow out. Intense, localized tenderness and hypersensitivity to cold temperatures should also prompt an evaluation to rule out conditions like a glomus tumor.