"Bloody Discharge During Pregnancy
Bloody discharge during pregnancy/lactation is fairly common and usually not related to papilloma. During pregnancy and lactation, breast tissue grows rapidly and this can lead to duct irritation that causes bloody nipple discharge. This discharge should not interfere with nursing. If the discharge persists after lactation has stopped, it should be evaluated further. "
I took this from a breast health website. But, as with anything, if you are worried, get it checked out, if only for peace of mind.