I'd be interested in speaking with you, I am a Mass WC atty.
Since you were already paid benefits there is no staute re re-openiong claim- it can be done as long as you have evidence that you still hace a work related condition causing disability or need for treatment.
Claim can and should be re-opened. I can be reached at 978-745-0914
The wc insurer may argue the problem stems from the car accident; if you aggravated the injury at work and your doctor backs you up you should be entitled to wc benefits. Consult an atty who can advise you what the proper causation standard id in your state.
No for two reasons
First the statute of limitations bars an action from 4 or 5 years ago
Second if the defendant was your employer your only remedy is workrs comp
An employee cannot sue his or her employer for injuries, only for workers comp