Your top priority is your well-being and safety. You need to move to safety and call 911 (or ask someone around to do it for you). Even if you don't feel hurt, you should still have a proper examination from a medical professional. After an accident your adrenaline is rushing and you may not feel injured when in reality you are.
Remain at the scene until the police arrive. It’s important to have a police report to substantiate your claim. The police will investigate the accident and document what occurred. This is particularly important if you intend to file a claim for damages with the driver’s insurance company.
Gather any evidence you can and take pictures of the scene of the accident, the vehicle(s) involved and of your injuries. Pictures of injuries, the accident scene, and the car are essential elements to your future case.