Mysterious red mark on baby??

My toddler son (14 months old) came home today from daycare with a strange oddly shaped red mark along the bridge of his nose. It's flat and evenly red. There's no bruising and he doesn't seem bothered by it.

He doesn't wear glasses or sunglasses or anything on his face. He's not acting sick (although he is teething).

It was really hot out today. But if it's a sunburn I don't understand why it looks like a patch.

If he fell on his face, I think they would have told me. Maybe not. Plus the bridge of the nose isn't really where he would have landed if he fell.

I did my best to get decent photos, but it wasn't easy!!! He was not loving the flash.

So- my question - have you seen this before ??

Any guesses as to what this might be ???