well I am no expert by any means but that lump is not normal.
and I think that is a male. I think I see the gland that is behind the front leg that males
get.
I am glad to see that you have sand as substrate, what kind of filtration do you have and
I also see that you have a lot of snails.
I can't tell if that is a parasite or some kind of infection.
I would Email Dr. Fry dr.frye.dvm@sbcglobal.net