Mastoid is a bone located just behind the ear and its air space is connected with the space of middle ear.So whenever infection occurs in otitis media
,it involves air cells of the mastoid.Mastoid air cell disease
is usually diagnosed by a CT which reveals opacification in the air cells.
This opacification is due to either infection or inflammation of the tissues.
Such infections usually cause symptoms like tenderness at mastoid,thick purulent discharge,low grade temperature,headache etc.
But since your only symptom is a headache without any other sign of infection,acute mastoiditis
as a cause for your headache is ruled out.
You must consult a neurologist
for evaluation of cause for your headache and it's treatment.