Ever been in an auto accident? Many accidents which are low impact and commonly brushed off as "not that bad" are actually much worse than conventionally expected. When a car is hit, the damage done to the car actually absorbs the hit that the person will receive, which means that when you are in a low impact collision, and there is little damage to the car, your body actually absorbed more of the impact.
This acceleration/deceleration action can lead to many long term problems when untreaed, including whiplash, nerve damage, and chronic headaches to name a few. Commonly a car accident victim will take some over the counter medication for a few days, and when the pain is gone, will assume that there was no damage. Unfortunately, all that is doing is blocking the body's signals that something was injured, and that can lead to injuries that never heal properly. If you have been in an auto accident, no matter how fast you were going, go make a chiropractor appointment for a checkup. You will be happy you did.