A few days ago I noticed this strange mark on my inner thigh. It's a small (less than 1cm) circular spot, like a blood spot. Over the last day or so it has developed a paler inner circle. A few months ago I had a similar, smaller mark in exactly the same place. That went away after a few weeks and I thought no more about it until I noticed it had come back a few days ago. It doesn't hurt, it's very slightly raised but not itchy or scaly. Any ideas what it might be?