Am being treated for bulging disc pressing on sciatic nerve pain shoots back to front then down inner thigh to knee can this cause rash on inner thigh?

Unusual. It would be unusual for a disk to create a sciatic nerve neuropathy, but more of a root problem, which seems to correlate to your symptoms more. However, a rash would be unusual to be caused by such a nerve problem. Please see your physician to be sure it is assessed and evaluated.