If I wronged someone, and then removed the wrong from him, do I have to apologize to him?

You have not specified the nature of the injustice. However, if you have wronged a person by taking their money, you must return the money to them without informing them or seeking their forgiveness. If the injustice was backbiting, then what is obligatory is to repent, seek forgiveness for them, and frequently mention their good qualities. This is sufficient without seeking their forgiveness, according to many scholars. If the injustice was of another kind, then explain what you did so that we can clarify how to repent.