All seems perfect until I noticed that something looks terribly wrong, new buddy has this kind of lesion on its back.

Years and years keeping hermit crab, this is the first time I see something like this. Is it what I think it is? I do not want to harm and risk my family with a parasitic worm that may be able to infect human. Or is it just an open wound that exposed its muscle? Ladies and gentlemen, do you have any pieces of information about it? Even a chunk will come in handy... I really need it at the moment, Thanks!