The Chofetz Chaim offered the following explanation of this verse:
When the brothers had initially arrived in Egypt, they were treated harshly by Yosef, who accused them of being spies. The brothers were startled by what was happening to them, and they asked one another: "Why is this happening to us? Who among us is guilty of a sin that would have brought this upon us?"
On the brothers' second trip to Egypt, they once again asked one another: "What is this that Hashem has done to us?"
However, continued the Chofetz Chaim, when the brothers heard but two words: "Ani Yosef" - I am Yosef - all of their questions were answered. Suddenly, everything was clear - all of their misfortune had occurred as a result of having sold Yosef.
Today, as well, concluded the Chofetz Chaim, there are many people who question the way that Hashem runs His world. "Why do the righteous suffer?" they ask. "Why can the wicked prosper?"
However, at the End of Days, when the entire world hears Hashem utter but two words: "Ani Hashem" - I am Hashem - all of the questions will vanish.
Source: Rabbi Yisrael Bronstein