From Longman Dictionary of Contemporary Englishit’s/that’s not my problemit’s/that’s not my problemspokenDON'T CARE used to say rudely that you are not responsible for dealing with a particular problem and are not willing to help ‘We’ve got a serious staffing shortage.’ ‘That’s not my problem.’ → problem
Examples from the Corpus
it’s/that’s not my problem• It's not my problem if she won't listen to reason. 