I do not think it is possible for him to poo it out since it's of a quite large gravel for his size. He is still swimming; i dont know if he will live.
I will very much doubt he will die. He can survive with that in his stomach if he cant pass it he will probably throw it up in a few months. I know people with large catfish who have eaten suction cups and all sorts you just have to wait till the trow them up.
But he will be in pain for a few months then. What is the peice of gravel blocks his "below" where he poos. That way he cant digest anything. So should i stop feeding him for say a week or so? From what i see, he was swimming ok up to now