What does having a bruised knuckle mean?

Having a bruised knuckle is a common outcome of punching a solid object and it refers to bruising in the front bone covering the bones that join finger to hand (interphalangeal) or hand to forearm (knuckles).

In other words, it happens when an individual punches a wall, floor, another individual with little protection for knuckles of a closed fist which results in bleeding under skin which forms bruise.