can you see any blood on/ under the finger that hurts?
I ask becasue I have a few things I do that
as for how to stop, is their anything you can think of that might cause the same satisfaction? (but not injuring yourself?)
something like punching a pillow, squeezing a stress ball, that kind of thing- or what about things that keep your hands busy- jigsaw puzzles, books, I own a fidget spinner and it's great, their's loads of nicer distractions you could do