I notice that this happens to my ds if he has too much citric acid (oranges, tomatoe sauce, etc.) I would dab some diaper rash cream on it at night and see if it helps. Hydrocortizone cream may work too. I have used that before. Good luck!!
This happens to my boys all the time. I just have them soak in a soapy tub, and apply an over-the-counter antibiotic cream afterwards. It usually is much improved after one day, and will clear up completely in couple days.
It's what my circ'd husband called that area! What do I know, I figured he knew what he was talking about seeing as he has a penis and I don't. He's did the first potty run of the morning so he noticed it first.
Anyway, it seemed to get better as the day went on. Thanks!