What should I do if I got hit from behind and I didn't have any insurance but the person that hit me has?

It's often a good idea to retain a lawyer. But regardless, you can contact the police and get the name and address of the driver who struck you. At that point, it's a good time to consult a lawyer so that you will know the different items of damages for which you can make a claim. Or else, you could represent yourself and set out to the other drivers in sure exactly what happened, stressing all the parts of the events which show that they're insured driver was at fault. You would then presumably make a demand for all of your losses trash including repair of the car, your own physical and medical and hospital charges, now and expected in the future, your loss of satisfaction in life caused by the accident, and your fission's best estimate of how long you will lose that capacity. Of course your own medical bills and lost wages are a significant part of the whole. Returning a skilled personal injury lawyer is almost always a good investment.