duty calls

A phrase used to indicate that one must return to work or do a particular task. Well, it was nice chatting with you, but duty calls—I've got to get back to those spreadsheets. A: "Hey, can you help me unjam the printer? B: "Duty calls!" Duty calls—this garage isn't going to clean itself!

duty ˈcalls

used to say that you must do something that cannot be avoided, especially when you have to stop doing something pleasant: Ah, duty calls, I’m afraid — I really must go and finish off those letters.