There a ball bearing size bump in my thumb knuckle where i hit it a month back. i repeatedly hit my thumb and now it hurts when pressed..

Lump thumb: Could be several things. Maybe you broke it and what you feel is the bone callous forming at the break site. Could be a traumatic ganglion cyst at the joint. Could be a traumatic tendon sheath cyst. Could be several other things. Bottom line you need to see healthcare provider and have this checked out. Hope this helps. Best of luck. Dr R