Hi Haley
Black is not good. In spite of the common phrases ?black eye? or ?black and blue. Ecchymosis is not black. Initially the lesion starts out as bluish. As the blood cells degenerate, the hemoglobin that hey contain changes to bilirubin and then hemosiderin. The accompanying color change is from blue to green and purple. The final result is a brownish hue. Granted, it is sometimes difficult to tell the mixture of purple and green from black, but if it is black and expanding at the same time, then it is unlikely that this is only from blood. The mixture of fresh blood into and around the lesion should give up a mixture of colors.
Bottom line, get it checked out now, probably by a dermatologist.
This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.