I have been hit on knee,i feel no pain and can walk ,run,jump normaly.mild pain when i rub knee against something hard.injury or anything serious?

Contusion: Your lack of symptoms running and jumping is reassuring that the knee joint itself hasn't been injured. Apparently there was a spot on a superficial area of the knee that was bruised and this contused area is still somewhat tender to touch. Bone or patella contusions slowly heal but consult a physician or orthopedic specialist if tenderness persists or worsens.