The danger of cooked chicken bones is internal perforation - if he is well, then you have been lucky. I used to feed cooked chicken bones to my first dog also, many years ago, not thinking anything about it. He was fine, but as soon as I learned how dangerous cooked chicken bones are (or any cooked bone), I stopped. Just not worth the risk.
You can, however, feed raw chicken bones - they are quite soft and dogs can digest raw bones, but not cooked bones. I feed my dogs a raw diet, raw chicken bones and all, and they are doing just fine.