Promptly rang nursery who said they don't know how it happened, was only four babies in today and they didn't see DS cry or anything like that. I've text a pic to my friend who is a qualified nanny and she thinks it looks like a pinch mark, so of course, there is the possibility of a child starting down the pinching route.
However, I'm still really upset and worrying whether I've done right thing putting him in nursery, guilt etc!
Any similar experiences?