Simply ask him if you offended him in any way and apologize if you did.

If you said something "offensive" to him in your response, then that is probably what it is. Even though he is a guy "friend" he may have liked you as more than that. Which is why he asked the question. The only way you will truly know, is to ask.

Well, do you like him? (Meant to put in comments section)

From your comments at http://www.answerbag.com/a_view/2739553 , to me, he was trying to find out if you liked anyone else. If so, he wouldn't have tried to ask you out, being apparently shy toward you, himself. It may not have been the "you're worse than someone's parents", but your tone of voice when you said it. I'm sure you were exasperrated, and sometimes when we're in this state, we don't realize how we come off. Your best bet is to sit down with him, alone. Tell him you don't like what seems to have happened between you... You've noticed a major change in the way he acts around you since that conversation, and you REALLY want things at least back where they were before. ASK him if something you said, bothered him. If he says, "No", ask him if it was HOW you said something, because obviously, to you, something IS different. You may have to "pull it out of him", since guys are reticent to tell girls their emotions for fear of rejection and ridicule. It sounds to me like you scared him a bit. The bickering is defensive on both your parts. If you like him, tell him whether you like someone elsewhere or not, you truely value HIS friendship, and don't want whatever's between you, now, to wreck that. AND, if you like him, and want him to ask you out, TELL him that... "I really DO like you, you know... And THOUGHT you were going to ask me out... I'd have said, 'Yes', but then you backed off. If you want to try again, I'm willing... Are you?" Be prepared, though. You may have wounded his ego a bit more than you thought, and he may need some time. Meanwhile, if he doesn't ask you, soon, don't sit and wait for him. Go out with other guys. If/When he's ready, he'll ask, and jealousy CAN be a great motivator. (Don't throw those other guys into his face, but if he knows you've been going out... Just don't do anything you wouldn't NORMALLY do.) Good luck. ;-)

Presumably you are very young because the obvious solution is to ask him if there was anything you said or did to change his attitude toward you. If so ask what that was and you can then decide if you should apologize or move on.

maybe you should ask him what happened

Cant help you. Im not responsible for you speaking without thinking or speaking without social filters. I have no idea what you said. You know what you said go deal with it.