I certainly wouldn't assume it's columnaris. That has a stringy, almost fuzzy look to it. It can sometimes be mistaken for a fungal infection, but probably won't present the way you are describing.
If it is granular in appearance, it could possibly be the beginnings of an outbreak of ick. If so, you will know very soon, because you will see more and more of the little white salts. With otherwise healthy fish, this is easy to treat with salt and a heater. (There are many posts on this topic.)
Are you sure that they aren't breeding stars? They occur near the gills and sometimes on top of the head.
Sometimes, too, a pimple is just a pimple. Pictures and parameters are almost a necessity to try to diagnose anything in goldfish.