What can ease the compulsion to bite your knuckes until they are painfully swollen?

Finger joints such as the knuckles are connected by tendons. Constant "aggravation" of a tendon will eventually create a condition known as tendonitis. It could also be that you have developed osteo arthritis in the joint itself. Pain, swelling in any joint should be examined by your primary care physician. While treating the knuckes themselves is very important, it is also essential that the underlying compulsion to bite them is treated. The urge to bite could be a form of Obsessive Compulsive Disorder, a sign of extreme boredom or it could be indicative of a psychological condition that causes a person to physically harm themselves. This could also be way of diverting of denying emotional pain by converting it into something with a physical cause. Pease find a trusted friend to talk to if you are feeing overwhelmed, sad, angry or frustrated by events that are happening or have already happened in your life. If that is not possible, there are help lines available where you do not need to tell anyone who you are. I wish you all the best - help is available for you.