1 John 1: 9   If we confess our sins, He is faithful and just to forgive us our sins and to cleanse us from all unrighteousness.

In the verse above, the confession is to God, and He is the one that forgives.  We do, of course, commit sins against our family, friends, neighbours, etc., and we have to make right with them whatever we have done wrong.  In other words, we have to learn to say sorry, as any married person knows.  And God expects forgiveness from us when we are asked to forgive.  If we do not forgive, we cannot be forgiven.

Col 3: 12 Therefore, as the elect of God, holy and beloved, put on tender mercies, kindness, humility, meekness, longsuffering; 13 bearing with one another, and forgiving one another, if anyone has a complaint against another; even as Christ forgave you, so you also must do.

Mark 11: 25 “And whenever you stand praying, if you have anything against anyone, forgive him, that your Father in heaven may also forgive you your trespasses. 26 But if you do not forgive, neither will your Father in heaven forgive your trespasses.”

Matt 6: 14 “For if you forgive men their trespasses, your heavenly Father will also forgive you. 15 But if you do not forgive men their trespasses, neither will your Father forgive your trespasses.

The passages above very clearly tell us that our forgiveness determines whether God can forgive us.  In most cases we find it very difficult to forgive, and only as we surrender to God and allow Him to change us, can we forgive.  Our forgiveness of others is only between them and us, and not a public issue.

But one thing we have to understand is that any sin we commit, is committed against God.  Look at the passage below where Joseph is being seduced by his master’s wife, and instead of seeing it as a sin against his master, he views it as a sin against God.

Genesis 39: 7 And it came to pass after these things that his master’s wife cast longing eyes on Joseph, and she said, “Lie with me.”
8 But he refused and said to his master’s wife, “Look, my master does not know what is with me in the house, and he has committed all that he has to my hand. 9 There is no one greater in this house than I, nor has he kept back anything from me but you, because you are his wife. How then can I do this great wickedness, and sin against God?”

Another example is David’s sin of adultery with Bathsheba, another man’s wife.  When she becomes pregnant, he murders her husband.  When confronted with his terrible crimes, he confesses to God:

Psalm 51: 3 For I acknowledge my transgressions, and my sin is always before me.
4 Against You, You only, have I sinned, and done this evil in Your sight—
That You may be found just when You speak, and blameless when You judge.

So public confession is only necessary if the sin was a public sin, but whatever sin is involved, it always involves repentance and confession to God.  Our sins are against God, and we have to confess to Him, after making it right with anyone we have wronged.  As the sin is against God, the whole issue is therefore an issue between Him and us, and He forgives us and cleanses us, and gives us the great gift of salvation.