I’m sorry to hear that your fellow Ash ate a chicken bone.
I assume that he ate the bone a few days ago and is now trying to pass the bone fragments and likely a larger, firmer and drier stool than usual due to the bone fragments and this is painful for him.
To help I recommend starting with a vaseline (or any generic petroleum jelly) sandwich. Take a half slice of whole wheat bread, slather with vaseline as you would peanut butter on a slice of bread, cover with a second half slice. Feed it to him piece by piece or he will make a huge vaseline mess. This adds fiber to cushion fragments and soften the stool and hopefully the lubrication makes the bones pieces slip rather than catch.
For the next few days, until the pieces pass, he'll need to be fed a bland diet with lots of fiber and fluids added in small meals several times a day, 4 to 6 meals is ideal. We do this so the bone pieces are surrounded, the gut isn't irritated contracting on just bone and the increased fluid intake keeps his stools softer.
A homemade diet for this is 1/3 boiled hamburger or white, skinless chicken, all fats and juices drained and 2/3 white rice. Add 1 tablespoons of canned pumpkin, (not pie filling, just pumpkin), to each meal for fiber.
You'll need to check his stools frequently for bone pieces in the next few days.
Signs that things aren't going well, and he needs an immediate veterinary visit, are vomiting, a tense painful belly, lack of an appetite, a fever (more than 103.5F rectally) and lethargy.
If you aren't seeing a stool pass in the next day or two a veterinary visit and an abdominal radiograph to see where the bone pieces are is an option. If it doubt at all that things aren't going well it is always best to have him checked. He may need an enema and manually breaking the stool down if the bone pieces have become compacted and too large to pass easily.
Once the pieces are passed and he's feeling well then start mixing in his regular food, adding a little more regular and less bland at each meal. It should take a week to get him converted back to regular food.
Let me know if you have any questions.