Hello! About 4 days ago I noticed a perfectly round bruise on the inside of my left arm, with a white center. The center was slightly raised, but not painful or itchy. Since first noticing this "bruise" the center has become less white, more like the purplish color of the rest of the bruise. It's about the size of a nickle. I have no idea how I got this, or even what it is! Maybe an insect bite?