Welcome to this site. I was stage 3 IDC and went through 15 months of treatment, but I can honestly say I never felt any significant pain. I'm sorry that nurse told you that, and I don't know whether it's true or not, but if it's going to hurt that bad, I would think they could at least numb the area with a spray lidocaine, or give you sedation, and I would certainly ask the MD about that. Also, while you have lymph nodes all over your body, usually the ones they're concerned with are under your arm (called the axilla), not around your nipples. Hope that helps.
Hugs & prayers,