If you believe in your PiXiu, then he will become your amulet. So when certain accident happens to him, it’s probably he sacrificed himself to preventing something bad happen to you. If I were you, I will clean my PiXiu and keep him in a safe place. I don’t know what your PiXiu is made of, if its made by jade or precious natural stone, you can try to sink it in mineral water. If the crack is very minor, and you’re very lucky, the PiXiu might heal the crack by himself. I saw my grandpa did that once to one of his jade, and it healed by itself in a week!