Maybe. Headaches after a bump on the head are common. If it lasts more than a day or is accompanied by other symptoms such as dizziness, pain when looking at light, sensitivity to hearing, trouble remembering, trouble falling or staying asleep, or change in personality you should see your doctor to have her evaluated for a concussion. With concussion have your child avoid activity or sports until healed.
Maybe, maybe not. Children often hit their heads on things. If a child is behaving differently after a mild injury, she should be evaluated by her primary doctor. Sometimes an emergency room visit is needed, depending on the symptoms. Head bumps in which there is low-impact on the head, little crying, no changes in behavior and no headache after the first hour, etc..., usually don't cause internal injuries.