I have a pinkish something on my left breast it's been there for 3 weeks. is it a rash or something and how do i get rid of it?

Breast rash: Hard to know based on the description of this. New growths that are pink and bleed, hurt or grow and don't go away in less than about a month should be evaluated by a dermatologist to rule out skin cancer, although that is less likely in young people but melanoma can affect people of any age. Rashes that don't go away in a few weeks and don't respond to Hydrocortisone should also be checked.