Here is a scriptural prayer for when you feel you have sinned. No matter who you feel you have sinned against, ultimately it is against God and him only have you sinned against.
Lord, I’ve Sinned Against You Only
God, in your grace, have mercy on me; in your great compassion, blot out my crimes.
Wash me completely from my guilt, and cleanse me from my sin.
For I know my crimes, my sin confronts me all the time.
Against you, and you only, have I sinned and done what is evil in your sight; so that you are right in accusing me and justified in passing sentence.
True, I was born guilty and was a sinner from the moment my mother conceived me.
Still, you want truth in the inner person; so make me know wisdom in my inmost heart.
Purify me with hyssop, and I will be clean; wash me, and I will be whiter than snow.
Let me hear the sound of joy and gladness, so that the bones you crushed can rejoice.
Turn away your face from my sins, and blot out all my crimes.
Create in me a clean heart, God; renew in me a resolute spirit.
Don’t thrust me away from your presence; don’t take your Holy Spirit away from me.
Restore my joy in your salvation, and let a willing spirit uphold me.
Then I will teach the wicked your ways, and sinners will return to you.