Confession and repentance is between you and God (or someone else and God).
However: “So if you are offering your gift at the altar and there remember that your brother has something against you, leave your gift there before the altar and go. First be reconciled to your brother, and then come and offer your gift.” — Matt 5
So if someone has a just grudge against you, and you want to go to God, Jesus says to first be reconciled to the person. That isn’t always possible - we cannot always identify who we have hurt, and that person may not be available or may refuse reconciliation - but we need to make the attempt.
If WE are the ones with a grudge, our job is to forgive.
If we haven’t tried to be reconciled, will God forgive us? I don’t know of any scripture, but in my own life, I’d say the answer is yes - but he will also make me miserable until I make the attempt.
If that doesn’t help, perhaps someone else can give a clearer answer.
Very high priorities in my understanding of God’s view of Christianity and Christian life.
Henry Wright’s church can set aside a Saturday for an all day Communion service for extensive going to one another and insuring things are clear.