What does 1 Corinthians 4:4 mean?

Paul has described himself as a steward of God's revealed mysteries. A steward is a servant entrusted with managing something he does not own. That's why a steward must be found faithful as a person of high integrity.

Paul has insisted, though, that he does not worry about people's opinions of his faithfulness. It's not that he is arrogant. In fact, he said in the previous verse that he doesn't even judge himself. In essence, he is saying the only opinion that should matter to a servant is his master's opinion.

It's not that Paul has no self-awareness, at all. He thinks about how he is doing. He presumably follows his own advice to "test" himself (2 Corinthians 13:5). He reports that he is not aware of anything against himself, any lack of integrity or failure in carrying out his duties.

That doesn't mean he is innocent, though. Paul knows well the truth of Jeremiah 17:9, "The heart is deceitful above all things." His point in these verses is not that he's beyond reproach, or perfect, or that he thinks he's infallible. Rather, Paul is simply saying that no human being's opinion—even of themselves—matters in comparison to that of God. In the end, the only verdict of his work as a steward that matters is the Lord's, and Paul will wait for that.