This is a bruise. As you have rightly mentioned it is clotted blood. There is nothing to be worried about. Bruises are more prominent one or two days after the injury. They change colour from red to purple to blue and black and finally get absorbed by the body. It will take about 15 to 20 days and resolve spontaneously. If it increases in size for more than 2 days. Then you could get your wife checked for clotting disorders. She will need to undergo the following bood tests, platelet count, bleeding time, clotting time, PT-INR. If it is normal there is nothing to worry. Warm regards. Dr. Rajdeep Mysore. Chirag Hospital Bangalore