I have a mole on my left breast. 3 weeks ago it started to raise and turn red then overnight it turnef black. what could it be? it does hurt w little

Several things: Could be an infection , hemmorrage or worse a melanoma so you should see your doctor or a dermatologist very soon.

Needs an exam: It is hard to answer your question without an examination. Your description is concerning. It is concerning when moles change - change in size, color, become irregularly shaped, itch, bleed. Most moles are relatively easy to remove and test. Please see your primary doctor or a surgeon to see if this needs to be removed and tested.