nose looks black to me but if it is blue then yes it is a blue nose. Blue nose is just a color and means nothing more then that, it does not determine if a dog is pure or what lines it comes from just means it has a blue nose. Looks like either a blue fawn if the nose is blue or just fawn if the nose is black.
As for purity if there are no papers with him then more then likely it is a mix of some sort, as to what the mixes can be is anyones guess as many bully breeds do look very similar. You may be able to see traits better as he grows as well. More then likely if anything bad happens in the future or if BSL
comes into effect in your area the media, AC, and general public will look at him as a " pit bull", uneducated people will lump all sorts of breeds into that name.
Cute pups and congrats, Is this your first bully breed dog? Have you read up on them yet? tons of info here so if you need anything answered just ask, otherwise the search button at the top will help you locate any info a bit faster. Tons to read on here.