It almost looks like an absess or an ingrown quill. You'll have to wait though for someone with more experience to come along but I know that in most cases the mom and babies are supposed to be left totally alone or there is a risk of the mom stressing out and canabalizing the babies. If it ends up being something more serious though she may have to go asap, this is a very hard situation so Im not sure what is the best way to go. Im really sorry to hear about your experience and I hope all your hedgies are ok.