管好你的嘴小鬼
[guăn hăo nĭ de zuĭ xiăo guĭ]
This nickname can be seen as a humorous warning or reprimand, as if the person is reminding others to behave or be cautious with their words. '小鬼' refers to 'little devil' or 'brat', a teasingly affectionate term for a younger or mischievous person.