As we are on the topic of fingers, an Avulsion Fracture occurs when the ligament tears out the fragment of bone that it attaches to. The little grey lump near the second knuckle is the fragment of bone that the tendon has torn out.
Caused by an over under pass from half guard, and the opponent turned to their knees. Splinting and therapy for about eight weeks to recovery. Still a couple of degrees range of movement missing, but it works well otherwise.