Understanding Pea-Sized, Moving Bumps on the Head: Possible Causes

A pea-sized hard bump that moves on top of the head could be a sebaceous cyst. A sebaceous cyst is a non-cancerous growth that usually forms on the skin and contains sebum. Sebaceous cysts typically feel like small, round, smooth, moveable bumps or lumps under the skin, although they can feel firm or hard too.