What should you know about a bruised nail bed on a finger?

A subungual haematoma is blood collected between the nail plate and the nail bed after the finger is hit, crushed, or exposed to repeated pressure. The nail may turn red, purple, brown, or nearly black. Throbbing pain is common when swelling creates pressure under the nail, while a small bruise may be mainly a colour change.

The nail can loosen or shed if the injury disrupted its attachment. A replacement nail grows from the base, so the discoloured area gradually moves towards the fingertip as the nail grows. A split nail, open wound, or injury to the fingertip bone can occur alongside the bruise and may need examination.

Remove rings from the injured hand before swelling increases. Rest the finger, keep it raised when possible, and place a cold pack wrapped in cloth over the area for short periods. Do not put ice directly on the skin, pierce the nail, or try to drain the blood yourself.

Keep any cut clean and covered, and protect the nail from catching on clothing. Use an over-the-counter pain reliever only if it is suitable for you and follow the product directions. A clinician can decide whether trapped blood should be released and whether the finger needs an X-ray or splint.

Arrange prompt medical care if pain is intense or worsening, the fingertip looks bent, numbness develops, you cannot move the finger normally, or the nail is partly torn away. An open wound, heavy bleeding, or a crush injury also deserves assessment because deeper damage may be present.

Contact a clinician if redness, warmth, swelling, pus, or fever appears after the injury. A dark mark that was not preceded by an injury, does not move outward as the nail grows, or extends onto the surrounding skin should also be checked rather than assumed to be a bruise.

Ask whether the nail bed or fingertip bone may be injured, whether the pressure beneath the nail needs treatment, and how to protect the nail while it grows out. If the colour change appeared without a clear injury, ask what other causes should be considered and when it should be reviewed.