When you apologize you’re telling yourself, and others, that you’re principled, open and willing to learn and correct. It only enhances your reputation in the eyes of others.
Be quick to seek pardon. Never delay it even by a day. Say it in person, pick the phone or mail. Do it now.
It’s appreciated if the apology comes with no conditions – no ifs, no buts. And say it with all the genuineness and warmth expected of a friend. And most importantly mean what you say.