Romans 5:13 (CSB) In fact, sin was in the world before the law, but sin is not charged to a person's account when there is no law.

Romans 3:20 (CSB)

For no one will be justified in his sight by the works of the law, because the knowledge of sin comes through the law.

Romans 7:7 (CSB)

What should we say then? Is the law sin? Absolutely not! On the contrary, I would not have known sin if it were not for the law. For example, I would not have known what it is to covet if the law had not said, Do not covet.

The Laws tells us what is wrong, what is sin. If a person never knew that lying was wrong they would be ignorant of the fact that lying is sin. And then with the ignorance of the law God will not charge that sin against that person. I however do not know that anyone in the world could honestly saw that they did not know lying was wrong. Even before the law of Moses was written people had the knowledge of good and evil. The people who have never heard of God and have never known the Laws of Moses their sins would not be charged against them. But one day they will face God and see His glory and they will then decide to believe in Him or not. I want to be careful here. I am unsure about their salvation. If Jesus is the only way to Heaven can people who are ignorant of the law and of Jesus get to heaven? This verse seems to imply this because if a persons sins are not charged to their account then God could not hold sin against them. Therefore they would be spotless. I do not think this applies to anyone who is in the modern world, except to remote tribes in remote parts of the world that Christianity had not reached. The Gospel will be preached to these people before Jesus comes back and they will have a choice to follow Jesus or not. Only God truly knows the condition of peoples salvation. And only I can know my soul is wright with God. So I do not want to get hung up on weather people who are ignorant of the Law will be saved or not. But rather i want to focus on me because I know the law and am I doing the things God wants me to do and am I not doing the things God does not what me to do.?! 

John 15:22 (CSB) "If I had not come and spoken to them, they would not be guilty of sin. Now they have no excuse for their sin.

Ezekiel 3:17-21 (CSB) 17 "Son of man, I have made you a watchman over the house of Israel. When you hear a word from my mouth, give them a warning from me. 18 "If I say to the wicked person, 'You will surely die,' but you do not warn him -- you don't speak out to warn him about his wicked way in order to save his life -- that wicked person will die for his iniquity. Yet I will hold you responsible for his blood. 19 "But if you warn a wicked person and he does not turn from his wickedness or his wicked way, he will die for his iniquity, but you will have rescued yourself. 20 "Now if a righteous person turns from his righteousness and acts unjustly, and I put a stumbling block in front of him, he will die. If you did not warn him, he will die because of his sin, and the righteous acts he did will not be remembered. Yet I will hold you responsible for his blood. 21 "But if you warn the righteous person that he should not sin, and he does not sin, he will indeed live because he listened to your warning, and you will have rescued yourself."

It is our job to let others know they need Jesus. There are other times God will use us to reveal a specific sin in the lives of other people. Like Nathan did with David (2 Samuel 12:1-7) and like Samuel did with Saul (1 Samuel 13, 1 Samuel 15).