My fingers hurt at the joint? when i bend my fingers it hurts at the joint of the fingers? i use to hit the heavy bag a lot during boxing sessions.

See details: I certainly be related to low grade inflammation. This inflammation may result from repetitive trauma such as punching a heavy bag. Have it evaluated.

Overuse?: You are usuing your hands to hit a heavy bag, and your hands hurt afterward. Sounds like overuse. When you make a fist the knuckles are covered only by skin and tendon. There is no padding. Repeated blows to this area can cause inflammation of the joints which accounts for the stiffness. You need to back off the hitting until the pain IG gone, then use gloves before resuming.