if you must (do something)
If you have to (do something). This phrase usually indicates the speaker's reluctance. A: "All right, close the curtains if you must." B: "Thanks, the sun in my eyes was really bothering me."
if you must
All right, if you have to. Sally: It's late. I have to move along. Mary: If you must. Good-bye. See you tomorrow. Alice: I'm taking these things with me. Jane: If you must, all right. They can stay here, though.
if you ˈmust (do something)
used to say that somebody may do something but you do not really want them to: ‘Can I smoke?’ ‘If you must.’It’s from my boyfriend, if you must know.