The time taken for a bruise to appear depends on the cause of the injury and the severity of the injury. Bruises that appear within 30 minutes of an injury indicate a serious injury, such as a fracture, as stated by WebMD.
A person can get a bruise due to bumping into hard objects. Also known as an ecchymosis or contusion, bruises occur when the blood vessels under the skin rupture. Most bruises are not a cause of concern since they will get better with time. Depending on the severity of the injury, it may take 2 to 4 weeks for a bruise to get better.