I have "pimples" on my breasts. Dark red in color and pushed - blood comes out. Flatten after popping and kinda leaves mark. Should I be worried?

Doctor can check. Skin lesions (bumps, pimples, etc...) that pop with some blood, and leave a scar mark, should be checked by a primary care doctor or a dermatologist. A dermatologist can tell whether the lesions are a serious problem or not. Rashes are very hard to describe in words. A diagnosis needs a visual examination.