Heat rash?

🙃

My baby boy has what I think is a heat rash or irritation from his pjs being tight and hot. It’s on his inner thighs next to his diaper area. One side is worse than the other. I’m thinking it could be from the fleece pjs I have put him in but my question is... besides exposing it to air (which I just started doing today 🤦🏼‍♀️) what could or should I put on it? It seems to itch bc at bath time he scratches at it. I have been putting baby aquaphor on it... any suggestions or is that good? I also went up a size on his pjs in hopes that’ll help.