In my still less than 30 years, I have been involved in two car accidents.  The first was when I was nine years old; the second at 17 years old.  Like many, I was fortunate enough to walk away from both with no significant, immediate symptoms.  The first gave me whiplash; the second a nice little burn on the arm from the air bag.  However, three years after accident #1, I had lower back problems akin to what an adult would experience with a herniated disc (pain, numbness in my leg, and difficulty walking).  Four years after accident #2, I was in pain every day with chronic upper back, neck, and shoulder problems, as well as a lack of focus/concentration and digestive system that had slowed down considerably.  I was a mess. 

Accidents, be it of the auto or any other kind, frequently don't cause immediate problems, but they always do underlying damage that eventually finds you dealing with problems long after the accident.  Most people think that if you aren't knocked out, bloodied, or in excruciating pain after an accident, that you don't need to go to a doctor and get checked out.  While you may not require medical/emergency attention unless your symptoms are that severe, you need to be cognizant of the fact that unless you address that underlying damage, it will come back to haunt you. 

Regular physical trauma (falling down, childhood injuries, the birthing process) causes the body to break down.  The delicate structural balance between the skull and the top vertebra in your spine that protects your brainstem - the master control of every bodily process - often gets thrown out of balance when you're in an accident.  The brainstem malfunctions, which leads to various different abnormal conditions in the body.  The rest of the body structurally compensates, which can lead to various different pain-related conditions from head to toe.  The longer the breakdown continues, the more problems result.  Car accidents are of such severity that they cause that breakdown to accelerate, potentially at a rapid rate. 

It is, therefore, important for you to get evaluated after an accident; it may just save you years of potential long-term problems by being proactive in the short-term.