From Longman Dictionary of Contemporary Englishin my humble opinionin my humble opinionspokenTHINK/HAVE THE OPINION THAT used humorously to give your opinion about something → humble
Examples from the Corpus
in my humble opinion• Excellently done nevertheless, in my humble opinion.• In my humble opinion, he should not be called upon for such justification.• In my humble opinion, Sarah is not so much interested in old relationships as new. 