Kim Jong Un won’t nuke China because he’s afraid of China... because China is much larger and richer than he is. and more manly.
North Korea’s not going to nuke anybody. Fat boy and his minions enjoy their perks, and they’re not going to take any chances of losing what they’ve got. What they’ll do is act insane and hope the other powers will swallow the bait and give them money to pacify them. Frankly, I think the Chinese are too wise to play that game.