i've moved many nems in the past and had a tear before... how did you tear the foot..? did you do it, or did you buy it like that...? i wouldn't have taken it home like that... it can get infected fast especially if it's in the bag with stale water...
anyways... right now just leave it alone... if it has two mouths, it might stay too mouths for a while like that... right now don't try to feed it or anything... give it a week... it could have a false mouth, and if it eats something there might not be a stomach and it will rot in there...
good luck...