First I'll spare you the lecture about how these fish are not good captives due to size.
If the bump is along the length of the body is is likely a parisitic wrom. The onlt thing that can be safely done is wait until it emerges, move the fish and and keep changing water until you're comfortable no neotides are present. If it is a red blister kind of would, use a very light fungle med in 1/2 doses for three-four days