Red penis - nappy rash?

Put DS in cloth overnight for the first time last night, and when he woke up this morning the tip of his penis loOked red... He doesn't seem in pain or anything, what could it be? I hope it's not nappy rash, he's never had it before and I have no idea what to do! Any thoughts? Could the night nappy have caused it?

My little guys sometimes just get a red penis and then it goes within an hour/a few hours. They've never seemed in pain with it.
I think if it was nappy rash his bottom/testicles would be red too.
Actually when my guys have had nappy rash usually their willies have been ok but their bottoms/testicles have gone red.

I'd leave him nappy free for a bit or actually just put him in a nappy and check the area throughout the day.