This is a complicated question, and I think it’s important to think through the things I say in light of your specific circumstances. Because I don’t know the particulars at all, have a think through how these things might apply. Please don’t think I am guessing at your motives - I am just trying to cover my bases so that you can make a wise decision!
1. Ask yourself: What are your motives?
Does the person you want to apologise to know about the wrongdoing or will it be news to them? Is this likely to bring them some resolution or will it only serve to upset them and clear your conscience? I’m not saying that you shouldn’t tell them, but I think you need to make sure that you can raise the issue and confess and apologise in a way that will cause the least possible hurt. If our goal is to love God, and to love our neighbors, as the Bible tells us, then we need to think about this, especially when you could be picking at old wounds. How is what you say likely to affect them? If what you say is going to cause them a tremendous hurt that they wouldn’t have felt otherwise, think hard about why you want to raise the issue, and think hard about how you can minimise the blow.
2. Remember: Honesty is God’s way
The first person you need to say sorry to is God. Satan is the father of lies. Denying our sin honours him and hurts our heavenly father. It sounds as though you have admitted that whatever you did was wrong, but make sure you pray to God about it and say you’re sorry. Also know that because of Jesus’ death on the cross, you can be forgiven for this wrongdoing. What great news!
Whether or not you need to disclose all of the past circumstances to the person you have wronged will need to be thought through carefully, and you can pray and ask God to give you wisdom to figure out how to approach it.
In general, when apologising, some things that might be helpful to remember:
1. It’s about the other person. Their response might be hurtful to you, but you are trying to do the right thing by them. This means not talking about how they might have deserved it and trying to graciously accept their response.
2. Take responsibility. It’s great that God has laid this thing on your heart to apologise for. Make sure that you take responsibility for your actions. It is so much more meaningful than making excuses.
3. It might be helpful to explain to the person why you have chosen to bring this up now after all these years. It might be helpful for them to know that you still feel bad about it.
4. Be prepared to make amends. Not knowing the particulars of the situation, all I can say is that it might be meaningful to offer to make amends, for example, if you stole something. Not because it makes up for what happened, but because it can mean alot to the person who was wronged.
5. Regardless of the person’s response, remember that if you have said sorry to God, then he has forgiven you.
I suppose in the end, in most circumstances, I would prefer to confess my wrongdoing to the other person. Lies are as much a sin as the original deed. But we need to always be sure that we are seeking the other person’s best interest when we approach or raise these things. Be gentle, be humble. Pray for God’s wisdom. I hope that this works out for you, and, if you do talk about this past event with this person, that God will be glorified by the way you conduct yourself.
Grace and Peace in Christ to you.