I have guilt and idk if I need to do this

A couple years back I bullied a kid, I just went to his place to apologize. I apologized but when I did his mom was asking what I said to him that was rude. I said I didn't remember specifically, but the truth was I did it was just an awkward insult so I didn't say it and now i feel guilty. She said she remembered yelling at me before for it so I'm assuming she remembers what I said. I'm wondering if I should go back and tell the truth about what I said but at the same time it's awkward and I don't think it even matters anymore.