Based on how serious they are, bruises can change in a matter of a few hours, days or even weeks. A moderate bruise would usually take around 14 days to heal up completely. Unfortunately, bruises in the lower legs take a longer time to heal. Bruises usually appear in body parts like the breasts or eye areas where blood can pool up easily. When a bruise occurs in body tissues or cavities, it is known as a hematoma, which is actually a health threat.