same here
i broke my knuckles when i punched my computer screen about 2 yrs ago..
it hurt like crazy for a couple of months, then it seemed better, but even up till this point when i hit hard enought it starts to hurt quite a bit.
so sorry for not being able to answer, but i too would like an answer to this question
it might help people to find out which knuckle or knuckles you are talking about. Mine happens to be my middle finger knuckle