Hard to say for sure what those bumps are, lots of possibilities. For example if they have a cottony look to them, then it is most likely fungus. Or they could be damage from an injury from sharp objects, a collision, or possibly from tankmates, which has perhaps has become infected. Or it could merely be the fish equivalent of warts, or possibly a tumor of some kind.
The most important things are that the fish has a large enough tank and really good water quality, i.e. no ammonia, nitrite, and nitrate or less than 20. You are right to worry about your other fish too, but keep in mind that infection does not often run rampant in a tank which has excellent water quality. Keep an eye on them for sure, and you may want to do more research on goldfish diseases if you see any changes. Good luck!