As Paul has been speaking about exposing sin for what it is in order to warn Christians not be get involved with it, and as he also spoke about not being so graphic in the way sin is described, now Paul makes clear that God will shine His light and reveal the "hidden things" of darkness. What Paul is saying is that people will be held accountable for their sins, a warning that should put the "fear of God" in sinners!! The light that blesses Christians with revealing truth to them and then sheds light on their paths throughout their lives, is also the light that brings sinners to a place of accountability to their Creator!
Revelation 20:12 makes clear that every unsaved human being will stand before God at the Great White Throne! God will examine all they have done from their worst immoral sins to their self-righteous behavior which they thought would merit their entrance into God's heaven! They will hear those awful words, "Depart from Me, you cursed, I never knew you." But probably the worse thing He will reveal is the opportunities each person had to respond to God's witness to their heart of their need for Him! Every tract handed to them, every time someone spoke to them about getting saved, every time they felt a "tug" in their hearts to turn to Christ will be brought out in the open.
There's much more to be said, but let us who know the Lord do whatever we can to lead as many people to Christ as we can! Remember, someone told you! That's why Paul said in Romans 1:14, "I am a debtor..." KJV. We who know Christ have a responsibility to do our part that others can meet the Light of the World now in this life rather than to have to face Him as their Judge at that awful Judgment Throne.