A bruise is a collection of blood due to broken blood vessels underneath the skin usually caused by trauma. It causes discoloration and swelling in the area. Bruises often induce pain but are not normally dangerous as most bruises vanish in 2 weeks time.
Sometimes bruises can be serious, leading to other more life threatening forms of hematoma, or can be associated with serious injuries, including fractures and internal bleeding.
If you experience any of the following you should see your doctor immediately as they may indicate serious underlying illness: