5 days post car accident. i hit my head and had a bump on it. scans on day of accident were clear, but now have a headache and fever?

Bad headache: If headache is horrible "worst headache ever" immediately go to Emergency Room to check for internal bleeding. Fever needs to be evaluated by your primary care provider. For a bump and lingering headache, consider a cranial osteopathic physician. Find one near you at cranialacademy.org. Prevention mag describes this therapy: https://www.prevention.com/health/a20428644/osteopathic-doctors/

Follow up: It would be appropriate to followup with a physician. You may have sustained a concussion. The fever may or may not be related to the injury.