What is a round quarter size bump on top of head that move or hurt child?

There are a few conditions that could cause a child to have a round quarter-sized bump on top of their head that moves or hurts:

1. Cephalhematoma: This is a collection of blood that forms under the scalp of a newborn baby. It is usually caused by trauma during childbirth and is not typically painful. Cephalhematomas usually resolve on their own within a few weeks.

2. Caput succedaneum: This is a swelling that occurs on the baby's head during childbirth. It is caused by pressure from the mother's pelvis on the baby's head. Caput succedaneum is usually not painful and resolves on its own within a few days.

3. Subgaleal hematoma: This is a collection of blood that forms between the scalp and the skull. It is usually caused by trauma to the head and can be painful. Subgaleal hematomas may require treatment to prevent complications.

4. Pilonidal cyst: This is a cyst that forms at the base of the spine. It can become infected and painful. Pilonidal cysts are more common in adults but can also occur in children.

If your child has a round quarter-sized bump on top of their head that moves or hurts, it is important to see a doctor to determine the cause and get treatment if necessary.