There are several causes of headaches behind the ear.  A headache behind the ear refers to any pain that originates from that specific area of the head. Though headaches themselves are very common, headaches that occur exclusively behind the ear are fairly unusual. This type of headache pain can have several causes from nerve injury to dental problems. The cause of the headache behind the ear will determine symptoms and treatment.With regards to dental problems. The temporomandibular joints (TMJ) can cause aching behind the ear and it usually accompanied by jaw pain. The temporomandibular joints are the ball and socket joints of the jaw. These joints can become inflamed and painful. While most people with TMJ inflammation feel the pain in the jaw and behind the ear, others may just experience a headache behind the ear.
TMJ can be caused by:
stress
teeth grinding
arthritis
injury
jaw alignment
If you feel you maybe having TMJ issues talk it over with your dentist. As a dentist will be able to confirm if in fact that is the case and help treat it.