check engine,HELP!

I have a civic, which I took the heatsheild off of the stock headers to clean. when I put it back on I forgot to reconnect the O2 sensor to the clip and I started the engine and the CHECK ENGINE light came on. I imediately remembered what I did wrong and turned the car off and reconnected. I started again and it still came on. I even left it off for quite some time but it stays on. What do I need to do, does a profesional have to reset it or something?

there are a few different ways to reset that:

1) use a scan tool (or pay the dealer to use theirs)
2) disconnect the battery (-) terminal for 30 secs
3) I forget what the other one is...

yeah, but is that normal to stay on, even though I reconnected the problem later? I could reset it by taking out a certain fuse but it dosnt make sense to me why the light wouldnt go off if I fixed the problem.

The light stays on because it noticed a problem and does not know if it was a fluke or a possibly recurring event. The computer is programmed so that you must check the car over for a problem incase it is a reccurring issue. But, since you know why the light is on you don't need to check the car, you can simply reset the fuse. It's merely a safety precaution.

you can also just pull the fuse for 5mins, and reconnect.

OK thats what I was thinking, its all I needed to hear. thanks, I already reset it by keeping the fuse out for like 20 sec