my puppy has a red pimple like thing, protruding from his anus.
I don't think it is an anal glad. Perhaps a hemorrhoid, although I understand they aren't all that common in dogs..
Can you tell me what it is?
HiMY guess would also be a hemorrhoid, this really isn't that unusual especially in small breeds who have a tendency to become consipated.
I'd recommend that you have your pup checked out by your veterinarian just to make sure it's nothing more sinister.
To help keep your puppys' bowels regular and prevent constipation which can cause this problem, check out my A Constipated Puppy page.
Best of luck with your pup.