A few months ago, I had a blunt force induced laceration to the back of my index finger at the knuckle (second from the fingertip). The laceration healed normally, but the finger is exceptionally stiff at that joint and painful to bend very far. I've begun trying to bend it further by force, slowly, but there seems to be little improvement. Have I damaged the knuckle joint itself, or the attaching soft tissue? I wouldn't care much about it except that it's on my left hand and I was, before this, a fairly exceptional guitarist but since the injury I'm unable to play at all. Is this likely to require surgery, or will the simple exercise I've begun restore it to close to it's former mobility?