Red neck/rash?

Abi • 22- Mommy to baby Hugo 06.03.19👶🏻💙

Does anyone know what this could be? It started a few weeks ago and it was just red raw in his neck, didn’t seem to be bothering him, I guessed it was just dribble/milk getting trapped in his neck so I’ve been bathing it with warm water and cotton wool a few times a day and putting sudocream on it but now it looks like it’s peeling? Is it some kind of rash? I’m going to try and get him into the doctors tomorrow but just wondering if anyone has experienced the same?