Do I need to retain an attorney for an car accident I was in?

I think getting an attorney for this would be an excellent idea;  you should not have too much trouble finding a lawyer who will take this case on contingent fee (a percentage of the recovery), so that you won't have to go into your pocket to pay them.  If there's a problem with figuring out who's at fault, that might make it difficult;  on the other hand, if you were tail-ended, most lawyers will take a case like this with a big smile on their face -- and they can often get enough more out of it, than you could by yourself, to still let you come out ahead even after their fee.  An injury that aggravates prior disc problems often end up with some permanency -- and that's worth money.