Your headache can be part of a group of symptoms in so called post-concussion syndrome.
This syndrome consists of a set of symptoms that a person may experience for weeks, months, or occasionally years after a concussion (a mild form of traumatic brain injury), but, it can follow after moderate and severe brain injury in accidents.
It's main symptom is headache,usually more intensive and frequent than before the accident and most of the people are symptom-free within 3 months of the injury.
If symptoms are not resolved by one year, they are likely to be permanent, though improvements may occur after even two or three years.
This syndrome can't be treated, but it's symptoms can be eased by certain treatments.
Talk with your physician!