I would most definitely report it going forward. As to correcting the omission in the past, I would discuss with AOPA Medical, AMAS, or an AME before proceeding. If you're up front about it I can't imagine anyone will throw much a fuss, but work through a professional group who knows how to handle these situations. I guarantee you that you aren't the first or last to do this.
Good luck. Keep us posted on what you do.