Lymphocyctis is caused by an iridovirus and considered self limiting and a very common disease of fish..
"If" your fish has it, it should be isolated from others for approx 6 weeks, until the disease runs it's course. Any environmental stressors should be removed.
Because it is a virus, just like our common cold, any medication would be of little use, and may even be detrimental.
But you would need a microscopic examination to be sure.
I would just isolate it, and wait.