We can name a few reasons why Pug pooches do that. The first one is very simple: it keeps its nose lubricated to cool off during the summer. Pugs don’t really have sweat glands (only the ones on the paws’ pads), therefore the only way to keep cool is to lick their bodies and/or their noses. That’s where the heavy panting comes into play as well.
Another logical reason might be that, while trying to lick their lips, Pugs end up licking their noses too at the same time. The reason why it happens is that these cute wrinkled creatures have a very peculiar facial structure: flat muzzles with snouts that are pushed back closer to the eyes. That’s why you see their long tongues reaching all the way to the noses.