He's a bit young for it to be a dilute problem, although you can't rule it out. More than likely more puppy than blue.
A skin infection is possible, more than likely more puppy related than dilute. Not uncommon for pups to get pyoderma.
More often than not, Vets blame everything on the dilute factor. Not always true so I highly recommend you educate yourself about dilutes. He will have a thinner coat than say a black/rust because dilutes just have less hair per square inch.
Because of the thin coat the first thing you need to look into is a dog safe sunscreen....after you get the bumps cleared.
I would put pet insurance pretty high on the list. It will more than likely pay for it's self.

Have a look around the forum, I think you will find lots of threads to help you. Can't find your answer, feel free to ask. Lots of knowledgeable people that have experienced skin problems of all colors.