Many times after a car accident people will have initial neck pain, are seen in the emergency room and treated. If the injuries are not life threatening they are sent home with some medication and told to rest. Unfortunately, many will start to have headaches, even if they have never had headaches before. Those with a history of headaches will find their headaches are getting worse.
Most of the time the headache will dissipate over a week or two and everything will be fine.