Call the police and cooperate with the investigating officer for he/she will later become an important witness.
If you are having ANY pain or discomfort, TELL the police so it is documented. If it is not documented, the insurance company will claim that you were not injured by the car crash.
Request an ambulance and go to the ER so that you can be evaluated & treated. The failure to do so could be adverse to your health and detrimental to any future claim. Sometimes symptoms don't appear until 24-48 hours after a crash. If that occurs, please seek immediate medical attention at that time. Protect yourself and don't give the insurance company any ammunition to deny your claim.
Remember, every motorist has $10,000 of medical benefits available under their car insurance known as PIP, so don't hesitate to get the necessary medical treatment because of money.
After you have been released from the ER, call a lawyer and learn more about your legal rights. Find out who's responsible for repairing your car, paying your medical bills and recovering any lost wages. It is an overwhelming ordeal and it cannot be done without legal counsel. Don't try and do it yourself. The insurance company hires trained adjusters and you likewise need a professional to deal with your claim.