You should file your claim with the insurance company that insures the vehicle that hit you. You file a claim by filling out the No-Fault forms sent to you by the insurance company. Note that you are not obligated to give any formal statement (other than what is requested on the No-Fault forms) about how the accident happened in order to file a No-Fault claim.
If you do not know who struck you or if the vehicle was uninsured, you may file a claim with your insurance company or any insurance company for a relative you live with at the time of the accident.
If you do not know who hit you, or the vehicle was uninsured and there is no automobile insurance policy in your household, you should file a claim with the Motor Vehicle Accident Indemnification Corporation (MVAIC).