Please answer if you are a Vet, or Vet Tech , or even if you just know what im asking. Thanks so so so much!!?

Saturday I took my dog, a Boxer/pitt mix to the vet to question a bump on the end of his back close to his hip bone. I tried to find it for her & I unexpectedly found 3 more for a total of 4. I was shocked to find them because I give my dog a health check everyday where I throughly check his body for cuts, ticks, & things out of the ordinary. He loves to go running through the woods in our back yard, so I thought maybe it could be a spider bite or something like that. Our vet said no it is not, it is probably a clogged hair follicle or a wart. She said it is commonly seen on er spaniels. The bumps weren't large enough to cause concern she said, but she gave me the option to have them sampled or to wait it out and see if they grew large enough to get a decent sample to send off to the lab. Has anyone ever seen this on their dog, or does anyone know what they are, and if it is something to be concerned about? I appreciate your response.