Nurse says it's fine but I dont think it is.

I have a 4 month old daughter and a couple of weeks ago when I got her undressed for the bath her belly button was all red and like crispy yellow stuff around it anyway I cleaned it and by time the morning came it cleared up, and I didn't see it again until Monday. When I got her up her belly button was stuck to her vest and all the crispy yellow stuff was there again and it was all red. I cleaned it all off and now theres still crispy stuff around it but its not red. I took her for her 4 month injections yesterday and I asked the nurse to look. She said theres nothing wrong with it and shes fine. But somethings telling me to take her back for a second opinion. Did this happen to any of your babies?