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in the side of face, head and neck
could be due to injury to a nerve or pinched nerve, an infection or a trauma. Hence it could be Trigeminal neuralgia, abscess in tooth, exposed root canal, internal ear infection, maxillary sinusitis, TMJ, migraine, herpes (recurrent) without rash or fibromyalgia localized to face.
It is difficult to comment beyond this at this stage. Do consult your doctor.
Hope this helps.