Headache is one of the commonest symptom of concussion,and along with other symptoms usually resolves within 3 weeks, although these symptoms may persist even longer.
When symptoms of concussion last longer than 3 weeks, and linger for weeks, months, or occasionally years after a concussion, the patient is diagnosed with post-concussion syndrome.
The severity of symptoms lessens progressively over time and the majority of PCS cases disappear after a period of time.
Headache is the main PCS symptom and can be of different quality than before the trauma, more frequent or longer-lasting headache.

Best wishes!
Marija