A few days ago I noticed a rectangular (or off square) purple (dark purple) spot on the back of my upper arm. At first I thought it was dirt or something because I couldn't recall anything happening to me or hitting me. I'd been out working in the yard. It is still there. I can feel a kind of bump in the middle of the bruise looking area, and there is discomfort if I press on it. I feel perfectly fine, otherwise and am quite healthy, active (jogging, cycling, tennis, swimming) at age 62. Female. Thanks.