Suggest Treatment For Headache Caused By A Minor Injury

My son was playing in his room earlier and apparently bounced off a ball and hit the side of his bed. He did not come and tell me about it immediately. However, before bed he complained about it hurting and told me what happened. He can breathe deeply without pain, but says yawning hurts. He also say that squatting and standing back up hurts and that going up and down stairs hurts. What should I do?