What works great anytime he's gotten red or raw wrinkles, is a slathering of antifungal cream. I actually had a conversation with a pharmacist once because I had monistat in my hand and she advised I go with an antifungal cream that people use for Athlete's foot - the one I have been using with good success is Walgreens brand Clotrimazole, a lot cheaper than Monsitat and within a few days, all redness, soreness is gone. I just slather some into the wrinkle and rub it in. The fact that Mr. D lets me do this easily makes me think it feels good and makes him not sore as well.
On a side note, I had a bad cold once, and my nose was all raw and scaley underneath from blowing it. Vaseline, skin creams, etc were doing nothing. I decided to use some of this cream under my nose, and the icky skin that had been there for weeks cleared up in 2 DAYS!! This is why I haven't ever used diaper cream on him because I don't think it has anything in it for yeast, which is what is making your baby sore.
Good luck!
Editing just to say my vet does not recommend creams for folds. Says to keep very dry and only use malaket wipes and antifungal powder.