My Adult Daughter Got A Bad Bruise On Her Breast

My adult daughter got a bad bruise on her breast during a game of archery tag last week. It was swollen, red and painfull at first. Now it is still painfull but looks more like a bruise and there seems to be a lump of about 1cm that looks like a fold under the skin. She worries that it will cause or has caused cancer. Is that possible?