He's carrying in inside of his shirt, like with a kitten or other small animal. Just in case anyone was wondering.

The broken heart makes no sense considering it's supposed to be a nostril, but it's so adorable that I honestly don't care.

Presumably the artist, like some others have, mistook the nose for its eye - this is also why there's fluid welling up at the bottom.

Or it could be accumulating snot. Maybe it's just really, really sick and needs to blow its runny nose.

Nah, in that case it would be accumulating at the bottom of the nostril rather than well below it.