Cyst? Pox? Need help with a bubble on my fish

[Ana]

Recently noticed my fish had a bubble-like cyst in it's body, and was afraid so I separated him from the pond just in case it was viral.
Its been around two weeks since, the bubble is looking a bit uglier than before, but he fish Is still energetic as ever before, and isn't acting sickly in any way.

I mean it's not normal but, is it normal? Is it safe for the fish and the others? Could it be a tumor or something contagious

 

[GBBUDD]

Unfortunately gold fish come down with these lumps with no rime or reason. I was actually watching a goldfish video just last night and a breeder said he ran two different preactive medications for all his gold fish and i have to admit he had some beauties, but he never said what he did but this will tell you there is some regiments that the pros do.

 

[Lisak1]

Yeah we've had a few fish get these random lumpy bumps - it doesn't spread to the other fish, but it did eventually kill one of ours when it ruptured. Is there anything you an do? I don't know - maybe there are fish experts who could help, but how much is it worth to you? Our fish (both past and present) lived a normal life in spite of the lumps.

 

[Ana]

Yeah we've had a few fish get these random lumpy bumps - it doesn't spread to the other fish, but it did eventually kill one of ours when it ruptured. Is there anything you an do? I don't know - maybe there are fish experts who could help, but how much is it worth to you? Our fish (both past and present) lived a normal life in spite of the lumps.

These two answers are reassuring, if there isn't much I can do about it apart from fish experts, and if it can live normally then I'll let it be. The fish was given to me by a friend, so not really sure how old they are, but I hope it will enjoy it's new place (they've been in quarantine for a while)
I was really afraid it would be some kind of contagious decease, as I've done that mistake once two years ago and it costed me the lives of a lot of fish. Im terrified of it happening again, thank you for the help!