What could this be?

6 weeks ago I noticed a white spot type thing on my ds finger so I took him to the Drs as I was worried it was a wart. He said it definitely wasn't a wart but 'thought' it could be a milk spot. He said it should go on it's own but if it was still there in 6 weeks then to bring him back and he would take another look. This morning I have noticed he another identical spot on his toe and the one on his finger is still there. I can't get another appointment until next week as it's not an emergency but just wondered if anyone had any ideas as to what this could be? The best way I can describe it is that it is like a hard yellow head without the redness, Any ideas? xx