How do I sue the other driver for the auto accident?

Do you have the insurance information of the other driver? Call their claims department and tell them what happened. Keep a log of all phone calls. Get a copy of the police report. Your physician will tell you about your medical condition. You don't need an attorney just yet. The insurance company will pay your medical bills if no one else is doing it right now. When you find out how serious (or not-serious) your medical condition is get a free legal consultation. See if there is a State Bar approved Lawyer Referral Service in your area. An attorney referral from there would be fine. It seems like you have an "open and shut" case against the insurance company. An attorney would get one-third without, perhaps, having to do much. So get unbiased advice.