For believers in Jesus, all our sin—past, present, and future—has already been judged on the cross. As Christians, we will never be condemned for our sin. That was done once for all: “There is now no condemnation for those who are in Christ Jesus” (Romans 8:1).
To punish His children would mean that God would invalidate the cross. Paul mentions that: "God made him who had no sin (Jesus) to be sin for us, so that in him we might become the righteousness of God." (2 Corinthians 5:21).
On the cross, Jesus became our sin. His body received the punishment for our sin that we deserved (Romans 3:24). That punishment, the Bible tells us was complete (John 19:30). It doesn’t lack anything. God doesn’t need Jesus on the cross and to punish us to make us right. God is not invalidating the cross.
However, that doesn’t mean that God doesn’t discipline us. God corrects us, disciplines us, and brings to bear in our lives sometimes even painful experiences not to get us back for our sin but to point us forward. To help us see that what we’re choosing to hold onto is inferior to what God has for us. God doesn't discipline us because we are bad, He disciplines us because we are His children (Hebrews 12:6).
Because of the sacrifice of Christ, God sees only the righteousness of Christ when He looks at us. Our sin has been nailed to the cross with Jesus, and we will never be “punished” for it, in the sense of being condemned. At the same time, God does discipline His children as any good father would.