What Causes Circular Patches On The Skin?

The other day what I woke up, I noticed a red circle on my arm with a blister in the middle. Like a dork, I popped the blister, which then turned into two more blisters. No pain, no itching burning or anything of the sort. Not dry or scaly. Applied neosporin and the blisters have gone, but the wound is now turning brown in color and leaving a brown residue on my bandaids. The red circle is still there though hasn't increased or decreased in size.