And watch the video here before you set about cleaning it again: http://food52.com/blog/3589-how-to-clean-cast-iron

Well, if it was my pan that you did it to, you'd better pack an overnight bag and catch the first train smokin'! But if you're going to stay and 'fess up to it, well, just re-season it. Good luck!

You can't permanently hurt a cast iron pan unless you hit it with a big hammer. As the others say, just reseason it.

Wipe it with a generous amount of olive oil and put in a warm oven for a while, then wipe clean with a towel.

Cook some bacon in it. When it cools, wipe it down with some paper towel and salt. Rinse it thoroughly and burn it dry. It's okay to scrub cast iron but don't use scouring pads or anything like that.