Ok if the engine temp is up to normal operating temp, and you're still not getting warm air, it's likely the cable behind the heater knob. Mine came off the other night (thanks to crappy 5th gen heater cables that are too stiff/tight). You'll have to take the radio out and the whole bezel and look up in the dash. You should see what looks like a bicycle brake / shift cable up there behind the temp adjustment knob. Chances are the little bracket that holds the jacket stationary and allows you to push / pull the cable inside the jacket has come loose. So all you need is a philips head to take off the little black bracket.
At this point I would suggest using needle nose pliers to bend the little nipples sharper so they can grab the cable better, and bend the bracket a little so it applies more force to the cable jacketing. When you go to put the cable back up there and screw in the bracket, you should have about 3-4mm of the cable jacketing overhanging towards the driver side. Tighten that screw good and tight without stripping and you should be good to go.
Edit: Also a quick way to test for this without taking out the radio is drop the glove box and turn the knob, the cable for the heater core / cold flap is right there, and it will move around if the jacket bracket has come loose.
-96 Accord LX Coupe
"If it's upside-down and burning... then you drove it too hard... and if it's not upside-down and burning, you didn't drive it hard enough."