what's this on my baby neck and cheeks

Suzy • Mother of a beautiful baby girl 🎀👶🏽👑
For the passed two days I notice a rash on my baby neck and cheeks and is not milk going down on her neck because she's a breastfed baby and she doesn't drip milk when she eats. How can I make it better her pedriatic told me keep it dry and if is not better by Monday to bring her in.