Catechism of the Catholic Church §2487 — excerpt
Every offense committed against justice and truth entails the duty of reparation, even if its author has been forgiven. When it is impossible publicly to make reparation for a wrong, it must be made secretly.
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.