Pimple Turned Black Bump. If you did not clean the area properly then could have been oxidation of the sebum left on the skin and in the follicle - basically a blackhead. The contents of the bump become oxidized as a result they turn dark to form a blackhead.

Pink or red facial bump small facial lump painful facial bump marble sized facial lump. Dark Pimple Formation Many dark pimples on the buttocks begin as inflammation or infection in a hair follicle folliculitis and can progress to nearby skin cells. A bacterium known as Propionibacterium acnes lives naturally on the skin.
This is the substance that comes out when you pop a pimple.
Little bumps in some areas but much larger circular dark red areas that turn to a dark black center. Pink or red facial bump small facial lump painful facial bump marble sized facial lump. Often the first sign of melanoma is a change in the size shape color or feel of a mole. Almost certain to aggravate the pimple.