I can't say that I've had this problem but as far as I know it's not possible for your delt muscle to hit a nerve from being over developed, I'm open to correction but that seems ridiculous. A pinched nerve is pain from a nerve being compressed in your spinal column. It may be possible that your front delt is too developed relative to your rear delt thus causing shoulder rounding this puts stress on the discs in your back causing them to be pulled out of alignment and hit a nerve. The pain from a pinched nerve is a symptom of an underlying problem which should be attended top medically. I would avoid heavy training until you are recovered, to avoid causing yourself a much more serious injury. I'm also wondering if the expert you mentioned is a doctor? Or any member of the medical profession because that does not sound like legitimate medical advice. I hope this essay helps you man and once again I'm open to correction.