A post-traumatic headache occurs after an injury to the head or neck. In fact, headache is the most common symptom people experience after a mild head injury. The pain may start immediately or up to a week after the injury. Some people still experience pain months after the injury. The headaches are caused by swelling or fluid accumulating in and around the brain.

Reference: Written by Otesa Miles, https://migraine.com/headache-types/post-traumatic-headaches/ , july 1st,2019