Things that will help with bruising would be the application of ice. It shrinks the capillaries. After 3 or 4 days, you can switch over to a warm compress and use it 3 or 4 times a day for about 15 minutes. Vitamins A and K help in reducing the redness. Regardless of what you do, your body will still need time to heal.
Vitamin B12 is responsible for the functioning of the nervous system and the brain and for the formation of blood. Sufficient intake of Vitamin B12 will make you less likely to bruise, but it make not help to get rid of bruises that have already developed.