I was wondering what this was I just bought a new San Pedro cactus from a nursery and I’m worried it may be fungus or something
to worry about. In photo. Cactus stands about a foot and a half tall. And maybe a few inches in diameter.
Yes the spots appear to be fungal infections, possibly initiated with wounding. If it's a recent purchase maybe talk to the nursery. See the section on physical damage in this cactiguide: