parasite?

Good afternoon, all. I recently (last week) setup a 29g as a growout tank for a severum and jack dempsey that will be going in a larger tank later this summer. I used a bag of ceramic filter media from my well established 55g community tank's filter. The JD is eating fine and seems to be...

So here's the thing, I've had this little guy for about almost 2 months now but out of no where he got this big lump on his neck and I'm scared, I just wanted to get people's thoughts on it and what to do, also he has a white string coming from his gills and I think it's just skin but I doubt it