OK, I'll try. First of all, hydrocortisone can't cause permanent damage. Temporary use doesn't generally cause any damage either. You probably saw some irritation, which you thought was damage. If your dermatologist thinks your penis looks normal, then the changes that concern you are probably just minor variants that you never noticed before because you had no reason to look so hard. This will probably seem unlikely to you, but I frankly can't think of what else they could be. If so, there really isn't any way to get rid of them. If your partners think it's herpes, you'll just have to tell them otherwise, because it isn't. My best advice is to stop looking at your penis and get on with your life.
Best.
Dr. Rockoff