A blood clot can arise in a finger from a pinching trauma, like being slammed in a door and bursting a vessel. Another cause is from the finger's being pierced, as by a wire, leading to a pooling of blood that eventually forms a large clot. Such clots can range in colour from red to purple to black, varying with time. Clots in fingers generally heal on their own.
Pooling of blood is sometimes mistaken for a clot. The treatment in either case is the same: prevent or break up clotting and promote drainage.
Apply a warm washcloth to the area several times a day. This promotes blood flow and the carrying away of pooling blood.
Keep the hand elevated.
Take aspirin or ibuprofen over an extended period to reduce clotting.
Consider going to a doctor (perhaps even a vascular doctor) if the clot is unresponsive. Your doctor can give you a clot buster to dissolve the clot (thrombolysis) and an anticoagulant to prevent coagulation (pooling of blood that can become a clot).
Let the doctor perform an ultrasound, if she finds it advisable. A clot usually will show up in an ultrasound. Sometimes patients misconstrue blood pooling for a clot, so the doctor may decide the ultrasound isn't necessary.
See a doctor immediately if you suddenly experience a reduction in vision or verbal ability, chest pains lasting more than a few minutes, shortness of breath or a spreading beyond the finger of pain or numbness. This indicates a clot has broken off and may be life-threatening.
Clots can break off and travel to your heart arteries, lung arteries or brain. Superficial clots like those in a finger rarely break off and cause problems. Deep-vein clots are far greater risks for separating clots. You also want to prevent a clot from blocking blood flow in your finger and causing gangrene, which might require amputation.