Heya!
I had exactly the same problem. I believe it was inside my left palm (fretting hand) , on the index joint closest to the palm. It was just a little knot, it didn't hurt, only when you pressed it hard, it didn't grow or anything...I thought it was some kind of bone growing there...I didn't really payed attention, it bothered me occasionaly, but after some time (I don't know how long) it was gone, and it never returned.
But if it is some kind of bone spur, and it really bothers you, I think you can have it easily removed with some local surgery. Visit a docter I'd say.
get better quickly!
