What Causes Painless Bruise On Hip?

Hi, I have a large, painless bruise on my hip. It's been there for just over 3 months now, but I honestly can't remember injuring myself. There is no reduction in size or colour. I'm probably worrying over nothing, since it was a weird bruise that my grandma found and it turned out she had leukemia. I just wanted to know if I'm being paranoid and this is normal, or should I get it checked out with my GP?