Puss bump on dogs ?

I was bathing my mini-dachshund, Hershey and he yelped and nipped me when i tried to clean his belly. When I took him out i looked and he had a small puss bump on the edge of the hole where his comes out. I didn't pop, but left it alone. It had white puss not green or yellow so I do not think that it is a severe infection or a bite of some kind. I'm not quite sure of Hershey's age since I adopted him from a no kill shelter. He was neutered about 3-4 days before I adopted him. And I adopted him on the 4th. I have never owned a male dog before and I am not sure if this is normal.