If the base of his skull gets pressed (where spine meets skull), even lightly, my husband gets a headache for a few hours. should we be worried?

Headache: A speculation from me is that your husband may have a benign process called a neuroma in the location cited above and that pressure on it induces the headache. Does gentle examination of this area reveal any abnormality? has an MD examined this portion of your husband's anatomy? has a simple skull x-ray been obtained to rule out an underlying bone lesion, or soft tissue lesion?

Headaches: No. The muscles and nerves are inflamed. Occipital neuralgia or cervical spondylosis (arthritis in the neck) can cause the headaches that you describe. Physical therapy and injections can relieve the pain. An MRI of the cervical spine may be necessary. See a headache or spine specialist.

Probably not: In the absence of previous trauma there's little with which to be concerned. Just to each side of the skull base are small nerve branches (one on each side) that can be a chronic source of headaches fir some people. This is termed occipital neuralgia. Obviously he has a very sensitive, irritable nerve(s). I'd just abide by 'consensus judgement' and avoid it. Cheers.