oh thats sad! you can take some fingernail clippers and snip a little bit at a time, if you look really closely you can see the quick, just like a dog's toenails. try not to hit that area! but i would say a little bit every few days is better. you can also put a rock or something in his enclosure that he can walk on every day that will help him keep his own toenails in check. the rock is also good for the beak if you feed him on that, his beak will help stay trimmed as well.
This is an unusual problem as they usually wear down on their own. I've never had to clip a sulcatas nails. Can you post a pic, so we can see what they look like?
How old \ big is the tort? It was probably raised for too long in a glass tank with poor substrate and fed a poor diet. How is the pyramiding? Any sign of mbd?
Giving the tort access to a nice sized yard where it can get exercise, dig, graze on good grass and weeds, get sunshine, etc will solve most of those kinds of issues...