闹别扭 is a separable verb (离合词) meaning 'to have a petty quarrel or to be at odds with someone over something small'. The verb 闹 can separate from 别扭 when you insert a measure word, duration, or other element: e.g., 闹了一次别扭 ('had a tiff once'). You can also ask 闹什么别扭? ('What's the quarrel about?'). It's commonly used for minor disagreements between couples, friends, or colleagues, not for serious conflicts.