About three weeks ago, a purplish blemish appeared suddenly on my upper left arm, on top of the bicep. It wasn't raised, was about five centimeters in diameter, was uneven in circumference, and had a pale center, about the size of pencil top. It cleared up after about a week. I use a tanning bed quite regularly, and I lift weights pretty regularly as well. I also had unprotected vaginal intercourse with a woman a few days prior to the appearance of the blemish. Can anyone enlighten me as to what this symptom could be? The HIV websites all say that if any sort of skin condition manifests during the initial infection stage, then it's usually a rash. I've been worried sick about it, and I can't find anything online that could help me pinpoint it.