It's OK, it was an accident

Jack has taken my words and twisted them again. Now anytime he does something bad (Knock Drew's hat off his head, knock Drew over, throw a toy and hit something etc. etc.) he says, "That's OK it was an accident." I think he thinks that as long as he says this phrase after the fact then everything is OK. Ugh! I guess we need to learn the difference between on purpose and by accident.