File a claim. Whether it's your fault or not, file a claim. Also, keep tabs on your physical health. If you start getting headaches or sore spots in the next day or two, go to a doctor and have it all checked out so there's a record of it early on. The adrenaline rush will eventually wear off (if it hasn't already), and what didn't hurt at first, may afterwards.
Since it's already too late to do so, just rest tonight. But as soon as you get up tomorrow, gather up the needed papers, and start making your phone calls. While I'm not 100% sure about a police report, I believe it would be in your best interest to file one before you contact the insurance company. Just get your facts straight before doing this. Once that's done, then call the insurance company that covers the car you were driving so all that gets started. The faster you get these done, the better. God knows I'm no lawyer or legal expert, but I believe those are the proper actions from what I've read.
Also, don't drive the car anywhere, and don't try to fix anything, until someone can come and inspect the damage for the claim.