Sounds like your re-circulation door has dropped down on top of your airbox.
Pull the fan motor underneath the passenger side glove box. There's 3 screw/bolts that hold that thing up in place.
Pull it down and stick your hand up into the plenum chamber.
The re-circ door will most likely be fallen down across the blower fan hole.
You can pull this out and then go the Heater Treater route as I did for a full repair.
When I did this repair to my re-circ door, I managed to refit the new replacement door without having to chop/cut any of the HVAC box as Heater Treater suggested.
The repair looks all stock from the outside