“And the eyes of them both were opened, and they knew that they were naked; and they sewed fig leaves together, and made themselves aprons.”
When Adam and Eve had eaten the fruit of the tree of the knowledge of good and evil, the Bible says “The eyes of them both were opened.” They had been given a commandment. It was just one commandment – that they should not eat of the fruit of that tree. Why were they given that commandment? In his novel, Perelandra, C.S. Lewis suggests that the commandment was given simply so that they could obey it. I do not believe it undermines the important doctrine of the Sovereignty of God to say that in order for obedience to be meaningful, there had to be the possibility of disobedience.
The opening of their eyes implies that they realized what they had done. Now, they must have previously been aware that they were not wearing clothes. But Genesis 2:25 says that they were naked and not ashamed before their sin. This implies that now nakedness brings shame, whereas their innocent lack of clothes did not. Now that they were sinners, they were not simply without clothes. They were now naked and ashamed.
Their first reaction to this nakedness was to make themselves coverings by sewing up fig leaves. This was their own action. By their own works, they were hoping to make themselves right with God. Of course, they would soon find that this attempt would not work. The important lesson that Adam and Eve learned here is that we cannot cover over our own sin.