Well, its very unlikely that you would develop a sinus infection from a head injury that you described (but perhaps not impossible). In my opnion, it could be merely be a general pain (like the one that you would feel if your hand was hurt instead of your head) or a neuorological disorder (please don't get scared it could be nothing as well). The best thing to assure yourself (if the problem is seriously bothering you) would be to take a CT scan image of the Para Nasal Sinuses (PNS)and the brain as well. For PNS CT scan is good enough but for the brain your doctor may even recommend an MRI scan. Hope that helps. Good Luck!