The shell is broken - it must be surgically put back, otherwise, if you leave it, it may not bind correctly. If the shell has maggots it has an underlying condition. It may have gotten hit by a car, but the bottom line is you can make it comfortable, but he will die soon. If you do decide to spend money on him, there is a high chance his shell and flesh will get infected. The shell is everything for a tortoise. You would have to immobilize him for months on end. However, I would try to take him to a wildlife sanctuary. They might decide to save him, but otherwise, it’s your call.