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.
A lawsuit would likely yield nada. If you were injured in the car accident due to the negligence of the other driver, that would be worth pursuing.
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.
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