Yes, God Knows Our Hearts

Next time someone has sinned and says, "The Lord knows my heart", be sure to remind them that the heart generates the actions, the actions prove the heart.

If you have sinned, then you have sin in your heart.

There is a remedy for this condition, that is to confess to those we have harmed and to God, then He will cleanse us of that sin. However, God will not cleanse anyone who refuses to admit their sin or pretends they have not sinned.

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

James 4:6-7 "6 But He gives us more grace. This is why it says: “- God opposes the proud, but gives grace to the humble.” 7 Submit yourselves, then, to God. Resist the devil, and he will flee from you.…"