We were all sinners once, but Christ has paid the price for our sins. Therefore we shall not be punished for them.
As far as I know, punishment can be either eternal torment or some sort of earthly affliction. Christians are obviously not going to hell. That God uses his rod to correct His children is maintained by all Christians.
Thus we conclude that sin does bear primarily unpleasant consequences on the Christian's life, which, however, should not be seen as punishment, but as a means of sanctification.
The questions are: just how exactly does God fatherly chastises His people? Is there a possibility of this "correction" lasting for the whole life of the person in question, or even consisting of or ending in the person's death, so that other Christians learn from it, or is it always meant to correct and sanctify that person only in this terrestrial life? Plus, if our sins are already forgiven and we shall not be punished for them, what is to keep us from sinning? God's chastening rod, or love for Christ alone?
It may be pertinent to mention the excommunication in 1st Corinthians, as well as the brethren who died("slept") due to improper behaviour at the Lord's Supper.
What should we conclude from those incidents? Regarding the first case, I ask if there can be something as "too bad a sin". We have all been taught that all sins are equal, yet apparently Paul excommunicates this brother due to his sin being considered terrible even by the pagans. As for the second case, it's hard to see their deaths as a means of sanctification, since they no longer live so that they can be progressively sanctified. Were they therefore punished? If so, was it meant to teach the other Christians a lesson?