Hi! I Was Involved In A Car Accident 6 Days

Hi! I was involved in a car accident 6 days ago! I was hit by another car from the back. I went to emergency room where I had X-Rays for my head, neck and back. The results came back ok. Yesterday, I started to feel upper stomach pain and a bad headache. I am wondering if this pain is related to the accident, especially my stomach pain. Do i need to see my physician or this is normal after the accident.

Thank You