How long after a vehicle accident can you sue the party at fault?

I was stopped at a traffic light in Bowie Md. when a large suv slammed into the rear of a company car I was driving. The jolt was enough that I had a headache right after impact. After going to the hospital for treatment I was told I may not feel any effects of the impact right away. I stayed home from work a couple of days then returned. The last few weeks I have noticed severe headaches especially in the mornings. I have scheduled a doctors appointment to follow up. My age is 62 and I am a male.