This just recently happened to my new gigantea. The morning after I added him to the tank, he got himself shredded and stuck in my Vortech MP10. I gave him a day to work himself free but I did help him loose, very slowly and gently, at the end. Fortunately, the damage was limited to his outer edge and not the foot or mouth areas.
I consider myself lucky as my nem is looking like he will make a full recovery.
So, there is hope that yours could recover too.