Thanks for the comments, he is a cutie
The last time I took him in I told the vet about the bumps and she said that he seems to have a poor immune system (he'd had kennel cough that developed into pneumonia) so she wasn't surprised. They ended up giving him antihistamine and something else before the next set and no bump or anything! Luckily he only has one more now, his rabies shot, and he'll be done.
Updated picture of him bugging our other dog for you guys.