I had a similar experience. I fell flat forward on a concrete surface last year. Left breast was very bruised. About 11 months later, there was still a knot where the swelling started right after the injury. The situation turned out well. I went in for mammograms, sonogram, and a fine needle aspiration. It turned out to be a resolving hematoma and fat necrosis resulting from the fall. The aspiration was a cake walk! I didn't feel anything really. So, have it checked out if the knot is still there after a week or two. At any rate, that knot needs to be removed. So, don't sweat it too much. I assume that you had your annual mammograph last year for the radiologist to use for comparisons.
Hi,
Most likely the injury to your breast has caused the bruising and the lump and this could very well be a Hematoma.
A bruise caused by injury is often associated with a lump and it can take some time to disappear.
However,if you are concerned and this lump persist, more than a week or two,I would advise you to have it checked out by your Doctor.
Best wishes...