Neck pain on the left side usually results from a benign cause, like muscle strain from sleeping in an awkward position. Sometimes, a more serious cause may be a tumor or rheumatoid arthritis.

Headache on the left side may cause generalized aching ... A migraine headache may throb and be worse on one side. The pain may begin around the eye or temple and then spread across the head.

But even if you’re a headache veteran who's able to tough out even the most debilitating episodes, there are a few critical ...

Pain on one side of the head (right or left) Pain on one side of the head ... Similarly, in the case of cluster headache, there is pain in the temple or on one side of the head.