孙子别给老娘玩心
[sūn zi bié jĭ lăo niáng wán xīn]
This translates roughly to 'Grandson, don't try my patience.' It represents a very blunt, no-nonsense attitude from an authoritative figure towards someone (not literally a grandchild) who might challenge or disrespect them, with the implication that further provocation could lead to harsh reactions.