There is no penalty left for you to pay. Christ absorbed it in full. Sin still carries natural consequences, and a loving Father still corrects His children, but correction is not punishment and consequences are not condemnation.
The Grace Answer
The word penalty is doing a lot of work in this question, and it deserves a careful answer. The biblical penalty for sin is death, and that penalty was real. It was also paid. Jesus did not make a down payment on it or reduce it to a manageable installment plan. He absorbed the whole thing. So when you ask what penalty remains for the sin you committed after being saved, the honest answer is unsettling in the best way: none. There is nothing left on the account to charge you for.
That can feel too generous, so let me draw two lines that keep it from being confusing.
Consequences are not condemnation
Grace does not suspend cause and effect. Lie, and trust erodes. Indulge an appetite, and your body and relationships pay for it. Those are consequences, built into the way life works, and God loving you does not mean He rushes in to erase every result of a bad choice. But a consequence is not God's courtroom sentence against your soul. It is the natural weight of the action, and it says nothing about your standing with Him.
Discipline is not punishment
Scripture does say God disciplines those He loves: “For whom the LORD loves He chastens.” But look at the relationship the word assumes. He chastens as a father, a son. Punishment is about paying for a crime. Discipline is about training a child you already delight in and have no intention of disowning. A judge sentences a criminal he is finished with. A father corrects a son he is committed to for life. Those are not two intensities of the same thing. They come from opposite places entirely, and God relates to you only as the second.
The penalty question was closed at the cross. What remains is a Father raising a child He has fully forgiven, and even His correction is an expression of love, never a threat to your place in the family. His discipline is never Him getting even. It is Him growing you up, the way a good father trains a child he could not love more, precisely because your place in the family was never in question.