How do yoyu realive pain in the buttocks because of the sciatica?

Try stretching, etc.: It might help to stretch, and move your body in the opposite way that you move it when sitting down to work. This would not only be likely to help the buttocks, but also your lower back, a true example of a place where chronic pain occurs. Pain from sciatica might need back/lower back surgery for relief or just pain meds. See your doctor to be sure.

Spine Pain Options: This chronic pain in the distribution as you suggested is the result of an irritated nerve or facet joints or other injury typically in the lumbar spine (low back) which are caused by herniated disks, spinal stenosis or degenerative disc disease, etc requiring further evaluation by a spine specialist and may be candidate for facet injections/radiofrequency ablation and epidural steroid injection.