My baby would stash uneaten bone behind her potty. It is possible the bone is just too hard. If he doesn't consume it during the night, I would throw it away the next morning and give fresh food.
Thank you for your answer. He is currently practicing eating bones and organs.
Recently he has left bones. So I chop the bones with a knife and give it to him. He does not eat much bone, so I am thinking of merging with supplements. He mixed the organ with mince and was able to eat it a little bit.
He is not very interested in food. It seems more important for him to play than meals. I'm troubled because he doesn't eat much, but I will continue to be patient...