Suggest Remedy For Tender Black Bruise On Knee

I had an itch on the outside of my knee and scratched it quite vigorously which resulted in a lot of pain and a big purple lump. After a couple of hours it turned into a black bruise. Now,a week later,its still as black with a redness in the centre and tender to touch.I'm wondering if my vein burst when I scratched it. Should I see my GP?