What could be done about a sprained finger that is severely bruised?

Consider a fracture: Severe bruising from a finger sprain heightens my concern for an avulsion fracture or a tear of a ligament or tendon. Simple sprains only need to be splinted for short time. Persistent symptoms should be evaluated by a physician. Better yet, have it checked now to rule out these more serious causes.

Splint or buddy tape: If you have an injured finger and the xray is negative you should immobilize it for minor injuries, i would buddy tape the finger to the adjacent one for more significant finger sprains or injuries, i would use an aluminum splint limit activities until symptoms resolve.