What Causes Lump And Yellow Bruise On Chest?

Hello, I was joking with a coworker while she was laughing she hit me in the chest with her fist. It hurt but I did not think much of it. The next morning I woke to a large bruise that is about 3inches by 4inches, the bruise was black, blue, yellow and green. I touch it and noticed a lump, about 1 inch in diameter. It has been about a week and a half the bruise is now green in yellow but the lump is still there. The lump is on my left breast and hurts when touched. I am trying to decide if I need to get this checked out, cancer maybe? I am a 28 year old white male. Thank you, Tommy