If you have been in an accident and think you might have whiplash, I would recommend receiving medical attention immediately and obviously the severity of the injury will dictate what type of medical attention you should seek.
But in more severe cases, there are high impact injuries from car accidents. Paramedics should be attending to you at the scene and evaluating you. Based on their evaluation, they will probably recommend you to go to the ER. You should follow through on this to be evaluated by a physician.
From there, follow the guidelines set out. But as long as there is no serious damage such as broken bones or ruptured discs, seeking out a reputable chiropractor would be to your benefit.
Receiving good medical treatment in the acute phase of care, the first two to seven days, is really important. It can really help recovery and shorten healing time.
If the trauma is less significant, I would strongly suggest the police report to be filed and then again, seek a reputable chiropractor with the guidance of your primary care physician to be evaluated and managed throughout the healing process.