Hmmm...as usual these things do tend to happen on a long weekend of public holidays, don't they?

DS's was moist when it appeared and over a period of about a week, it all kinda healed over and dried up to leave a small hard lump right in the middle of his belly button. I don't really recall finding anything on his clothes, though.

If you are concerned, perhaps try and get in to see a GP tomorrow? Otherwise, if it isn't bothering her then you can keep an eye out over the weekend and take her early next week? In the meanwhile try and fold her nappy back as much as possible to give it some air (if possible).