air conditioner surprise in 2003 honda accord ex?

My husband and I drove from Little rock arkansas to missouri for four hours in 110 degrees with the air conditioner going. He stopped at a gas station and I left the car running for about five minutes. When he didn't come out within that time I turned off the engine because I decided that someone must have stopped to talk to him and I was well aware that the car had just been though a lot of wear.

As soon as he began driving again the a/c only put out warm air. The heater definitely works though.

Could we be looking at major work on the car i.e. replacement of an expensive part?