Any exposure to cancerogenous matters over a sustained period of time heighten your risk to develop cancer later in your life.
So, no. Never back to normal.
However, the chance will get a lot lower. The main point is to get out of the risk group as fast as possible, that makes up over 80% of premature death due to cancer cases (a more drastic view is what the CDC says about the US: More people in the US die due to smoking caused cancer, than car accidents, HIV, illegal drug use, murders and suicides combined). After that your chances aren't as good as if you never smoked, but there is no real statistical step anymore when you stop before ~30.
