I banged my arm yesterday and it's come out in a massive purple/blue bruise which takes up a lot of my arm. The thing is I have my prom in less than a week and I have a strapless dress! I don't want to wear a scarf thing with it either to cover it.
Is there anything that would reduce the colour of it so I could conceal it more easily? Or even better get rid of it completely?

If you're suggesting any products, I need to be able to buy them in the UK. Thanks a lot, please help me!