tumor or growth

Hi everyone. I have a 75 gallon freshwater aquarium, 7.0 pH, nitrates less than 10ppm, 0 nitrites, 0 ammonia, everything is clean and well balanced. I do add some aquarium salt when I do my water changes. I have a 5 year old female silver dollar that began developing a pea sized lump in her...

Can anyone tell me if this a tumor or a growth on my pleco is it going to burst or is painful to the fish what should I do or is to big has grown this big within 6 months