What Does An Itchy Rash Around The Waist Indicate?

I have had a rash on my side, waist area, for several weeks. Sometimes the itching is uncontrollable. I ve tried cortisone creams, and have taken Benadryl. There is a small mole, almost like a perfectly round and lumpy skin tag. That has also become itchy and I have scratched my side and made the mole break. I thought it was a pimple at first, but it s still there. The rash gets smaller and almost gone, then in a day or two becomes to come to life again and spread to a larger area. Should I be concerned, should I call my doctor for an appointment? No rash anywhere else.... Thank you