Neck rash?

My 7 week old has a fold in his neck and when hes looking at you or holding his head up straight you dont notice under the fold. Well when he had his head I noticed some redness ans ive been wiping , and gave him a bath to clean it for 2 days. Its nit as red as it was when I first noticed it but it doesnt look good. When he's calm and awake he does seem like it hurts him when i touch it or wipe up under it so I'm not sure what to do.

Edit: his leg did the same thing in a fat roll for a few day I put baby powder on it and cleaned it and it went away.so I wasn't worried about his neck originally.