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It appears to be a growing tumor. There's nothing you can do for that. If it starts to affect the fish's swimming ability, best would be to euthanize the fish.
No, Unless the tumor is caused by poor water qualities which would affect all the fish in the tank, Tumors are not contagious but the reason why many fish get tumors is from bad breeding practices genetically and since this is a man made fish, there is no telling what practices were used to create those being sold.