I need help with facebook please?

I sent a private message to my dad yesturday, it was such a nasty message, i was so angry, and then when i calmed down i realised, and now i feel so guilty. He hasnt been online yet, and i really dont want him to read that message. I tryed gettin on his facebook but i dont know his p, and to ind out his p i need his hotmail p, so i tried to guess his secret question and its "my first car" and i have no idea what so ever. What should i do? I cant tell him i didnt mean it because he dont even know im capeable of being that horible.