How long do I have to file a case? I was hit by a car a little less than a year ago.

The time within which you have to bring a lawsuit in your state is 2 years for personal injury, so you have plenty of time.  If the at-fault driver has insurance, you should immediately file a claim with his insurance company.  If you don't have that information, you can file an uninsured motorist claim with your own insurance carrier and let them figure it out.  You will need to provide documentation of your injury including medical reports and bills from your health care providers.  If you are still having problems almost a year later, you should definitely see a physician and have a medical evaluation done.