'If you have a rash that persists over weeks, you have to get it evaluated,' says Linden. Likewise, if the look of a nipple changes, or if you notice discharge (and aren't breastfeeding), see your doctor. 'If it's outgoing normally and turns in,' she says, that's not a good sign. 'If your nipples are inverted chronically, no big deal.' It's the change in appearance that could be a worrisome symptom.