Bruised nail bed on the thumb: what to know

A slammed door, heavy object, pinch, or sporting impact can break tiny blood vessels under the thumbnail. The area may look red, purple, brown, or nearly black. Throbbing tenderness is common because the blood has little room to spread. The nail can remain attached, develop a crack, or lift from its bed. A dark mark can also move toward the tip as the nail grows, which helps distinguish an old injury from a new change. Green colour is not the usual appearance of fresh trapped blood and may reflect moisture or another nail problem; see the guide to [Discoloured Nails](/symptoms/nail-discoloration/).

Protect the thumb from another knock and keep the nail clean and dry. During the first day, a wrapped cold pack held against the thumb for short periods may ease swelling; do not place ice directly on skin. Elevating the hand can reduce the pounding sensation. Use a simple pain reliever only if it is suitable for you and follow its label. Do not pierce, drill, or burn a hole in the nail at home, and do not pull off a partly attached nail. A clinician can decide whether pressure needs releasing or whether a wound or fracture needs attention. Nail procedures are described under [Nail Surgery](/treatments/surgical-dermatology/nail-surgery/).

Arrange prompt medical assessment if pain is severe or worsening, the thumb looks crooked, movement is limited, the nail is split or lifted, or the fingertip has numbness, unusual paleness, or poor warmth. Seek care for increasing redness, swelling, pus, fever, or a wound that will not stop bleeding. An injury involving a deep cut, a crushed fingertip, or a nail that is largely detached may need treatment beyond home measures. People with diabetes, reduced circulation, or medicines that affect clotting should seek advice sooner after a significant injury.

Ask whether the nail bed or fingertip may be fractured, whether the blood should be drained, and how to dress any cut safely. You can also ask what changes should be expected as the thumbnail grows and when a review is needed if the dark area does not move outward.