Should I seek a Personal Injury Attorney?

I was t-boned at an intersection, the other driver ran a stop sign while I had no stop sign. I visited a chiropractor and was diagnosed with whiplash that she would like to proceed with treating. While it's true that I would like to receive medical compensation for the costs of treatment, my main concern is that the other person's insurance is trying to argue shared liability since their policy holder claimed that I didn't have my headlights on (which isn't true). Do I need an attorney or should I cancel chiropractic treatment since it's a minor injury and try to fight liability on my own?