good evening, headache could be due to multiple reasons- referred pains from decayed tooth, middle ear infection
, migraine , tension headaches , hypertension
etc. so already his vision in checked, so look for any decayed tooth, middle ear infection, check for fever and rule out sinusitis, rule out middle ear infection, he should take rest and hydrated well, lastly get his blood pressure checked( even though keeping in mind he is 9 yrs old.) . if all these are normal, need not worry, try with brufen syp , he ll be fine.