This sounds like an acute post-traumatic headache. Even mild head trauma can trigger headaches within 7 days of the injury. The headaches tend to last longer if you have a history of migraine. Post-traumatic headaches can look like any primary headache (like a migraine) and should be treated as such. However, if you feel like you are not improving, you should probably have a CT scan of your brain just to make sure there is nothing acute like a contusion that is causing your symptoms. Once something potentially harmful is eliminated via testing, I would have your doctor or a neurologist prescribe medicines for migraine which include triptans or even a short course of NSAIDs like naproxen or even a prednisone taper.