I Have An Approximately 4-square Inch Section On The Back

I have an approximately 4-square inch section on the back of my upper thigh that contains small raised red dots in a highly concentrated area. It is itchy and painful to the touch or when I sit on something and that area brushes against another surface. I don't believe I've been bitten or am allergic to any known substance. It first appeared 36 hours ago and doesn't seem to have changed in size or appearance since I first noticed it. In the past few hours I applied Allegra anti-itch cream but I'm concerned it doesn't seem to be getting better and remains painful.