Hi mum, sounds like it could be some mild eczema or irritation especially if the neck area is dry and baby is scratching it. I would try to keep the area moisturised with a gentle, fragrance free cream and also make sure sweat or saliva around the neck is cleaned and kept dry since that can make it worse. If it doesn’t improve or gets more red, spreads, or baby seems very uncomfortable, then better bring to PD to have a look just to be safe.