My kitten had crusty black stuff in the corner of her eyes from time to time. It goes away as they get older. It's just like the "eye boogers" humans get, except ours is like, yellow. xD
The stuff on his nose is most likely boogers, like the ones we get! See a pattern?
It doesn't seem that serious, but if anything new and more serious comes up, then you should consult your vet.