Have you tried a timeout before with Chachi after he bites or nips? Like put him in a place by himself for a little bit, a place he might not particularly like... Also, we've found that a stern "NO!" a few times in your best disciplinarian voice can help, or a spray of water mist (some Yorkies like this), or rattling of a few pennies in a can, can discourage a Yorkie from this behavior. Good luck with him!
