Why do I have a painful lump on the back of my head?

Why do I have a painful lump on the back of my head?
A bump on the back of the head has many possible causes, including injuries, cysts, fatty growths, inflamed hair follicles, and bone spurs. Bumps on this part of the body can be hard or soft, and they can vary in size. Injuries are a common cause of bumps and lumps on the back of the head.