I believe prazipro is used to treat some parasites, but not all. Before jumping to conclusions and medicating unknown ailments please post a better pic so someone can help identify what is wrong.
Lots of possibilities - internal parasites, a tumor or some other type of growth, an internal bacterial infection, or even a virus (Lymphocystis can grow over internal organs).
No way of knowing definitively without cutting the fish open, removing whatever it is (or taking a culture of it) and examining that under a microscope.
Practically speaking, you have two choices:
1. Leave the fish alone and hope it's natural immune system can resolve whatever this is.
2. QT the fish and start treating with a mix of medications (Furan-2/Kanaplex/Metronidazole combo is where I would start)
Option #2 is basically trial & error. Treat and see if something helps. Not ideal, but sometimes your only choice.
Marine C and garlic extreme will boost immune system and give your fish a better fighting chance of possibly beating whatever the growth may be...but also like said before it's trial and error at this point without a real diagnosis. Good luck im following along with hope for you!