What Would A Longstanding Round Purple Patch Below Left Big Toe Be?

I have this round red/purplish patch on the top of my skin it is about the size of a quarter it turns white when I press on it. It has small pumps that form a complete circle, I have had this for months, I went to the dr for it a month ago he didn't seem to think it was anything. But it is making me crazy cause it is so noticeable . when my foot is elevated you don't notice the purple just the bumps. when standing it looks like a complete perfect circle of purple skin? Its on left foot below my big toe, I am not a diabetic.. I have been searching on line for answers and am getting more scared than anything