I accidentally broke your pen, but no harm, no foul.
no harm, no foul
idiomAlthough technically a breach of some code or law may have occurred, there was no actual damage meriting punishment, apology or retribution.
Origin
disputed originFrom informal instances of sports, in which a foul is a formal violation of the rules.
You arrived ten minutes late, but since the meeting had not started yet, no harm, no foul.
Although the clerk processed the paperwork incorrectly, the error was caught immediately, so the manager declared no harm, no foul.