What does Paul mean by sin in Romans 7?

In Romans 7, sin refers to the old sin nature. Paul explains that he would not have known this sinful nature except through the Law, for the commandment exposed lust and condemned him. The Law itself is not sin; rather, sin took occasion by the commandments and produced all manner of evil.

Les explains that Romans 7 is tough, like 8th grade arithmetic story problems that boggle the mind until the answer suddenly comes out. In Romans 7:7 Paul asks, "What shall we say then? Is the Law sin? Is the Law something wicked or evil?" and answers, "Banish the thought." Les says the best explanation of sin in Romans is the old sin nature. Paul says he would not have known his old sin nature except the Law, for he had not known lust except the Law said, "Thou shalt not." The Law condemned this religious Jew who thought he was keeping it. But sin, his old sin nature, taking occasion by the commandments, wrought in him all manner of contraptions and got his mind broiling.

Romans 7:7

What shall we say then? Is the law sin? God forbid. Nay, I had not known sin, but by the law: for I had not known lust, except the law had said, Thou shalt not covet.

How did Paul become aware of covetous desire according to Romans 7:7?

Paul became conscious of covetous desire only through the law. In Romans 7:7 he writes that he had not known lust or desire except the law had said, “Thou shalt not covet.” The commandment exposed and made known the coveting that otherwise would have remained unrecognized.