What is this rash?

So I’ve had this rash on my neck for over a month now and I can’t get it to go away. It gets better then worse, then better....It happened because I was using retinoid and the cream reacted with the necklace I was wearing. It doesn’t hurt, it just itches. I put cortisone cream on it, but my nurse friend told me to stop putting anything on it and let it “dry out”. Anyone else ever had a rash like this?