A couple months ago after a hard session of punching mitts , heavy bag, and ground and pound bag work, the middle knuckle on my left hand started hurting really bad and was really tender. I took it easy for a little over a week and didn't hit anything untill the tenderness went away. However as soon as i started hitting the bag the knuckle immediately becomes extremely tender and started hurting after 10 or twelve hard punches. Ive started wadding up some guass and taping it to my knuckle under my handwraps, this has helped allot but something is deffinately still wrong. Everything looks fine to me, I will head to the doctor next week I suppose. Does anyone know what this might be?