You don't understand it because you are confused. Read Romans 8: "There is now no condemnation for those who are in Christ Jesus" - rather plainly stated don't you think? If the sins are forgiven through the blood of Christ, there is nothing to punish. The bible clearly teaches that. You need to post the scripture that supports your view (it doesn't exist).
My understanding of the passage you quoted is that there is no eternal condemnation which doesn't necessarily mean that we still don't have to pay for or be punished for the consequences of our sins, even though our souls have been cleansed of them.
A person can get a disease from committing a sexual sin. The sin can be forgiven right off but the disease remains and we all believe that God can heal the disease if he chooses to do so.