You should only go to the ER for emergency medical treatment, and it is not a substitute for seeing your doctor the following day. A lawsuit would likely be fruitless, but please discuss with a local malpractice lawyer in your state.
As the other attorneys have suggested, I would pursue the car accident claim, assuming it wasn't your fault. the malpractice claim doesn't sound very strong. You are always free to get your records and have a local malpractice attorney review.
It sounds like you cannot prove you were damaged significantly in the ER. So, there is not a good medical malpractice case. If you were hurt in the crash, and it was not your fault, you should see a lawyer.
This is a summary based on incomplete facts. You should not rely on it as legal advise. No attorney-client relationship is intended to be formed. You may call me 772-562-4570; email me firstname.lastname@example.org, or visit my website http://www.millerlawoffices.us
Sign up to receive a 3-part series of useful information and advice about personal injury law.