The most recommendable thing to do would be call a vet. Bumps on black moors can be credited for many things, like tumors, cysts, or swim bladder diseases. The only question I want to ask you is that... Is it falling over to one side when it's swimming? or maybe is it not swimming like a normal fish should?
I've never kept goldfish before, however I saw that no one replied to you yet and I wanted to help a bit
I'm so sorry about your black moor!