could be herpes smplex. Take some Acyclovir as advised and pandol if necessary for pain or apply cold sore
ointment. Get your blood checked for Herpes simplex
It coud be a bleed from duct, check if nipples are in good shape not everted.
How long has this been?? is it on both sides?
you have to rule out Breast Cancer
, by sefl examining and ultrasound
adn or mammogram. Consult your own OBG specialist.