I agree with Crickest about the size of the stone... if you actually saw him eat the stone and you know what size it is then you have to decide what the best options are in order to get your beardie the best care.
If it was a relatively small stone, I personally would stop all live feeders and give him unsweetened applesauce with a little olive oil and some warm baths to try and get him to pass it.
If it was a good size stone, then I wouldn't even hesitate about geting him to the vet. If the stone has jagged edges it could do some damage as it moves through your beardie.