It is sometimes possible to recover a clogged nozzle. The first step should be preheating the extruder to the operating temperature of the last used material. Then retract the filament and trim the end. With no filament loaded, make sure the feed gear is clean and unobstructed. Compressed air can be used to remove debris from the feed gear.
Then preheat the extruder to 50°C above the standard material temperature (250°C for PLA) and reload the filament. If the filament extrudes, extrude 100 mm to assure there is no debris in the nozzle. Then return the nozzle to the standard material temperature and extrude another 100 mm.
If the filament does not extrude, set the temperature to 10°C below the standard material temperature (190°C for PLA), then retract the filament 100 mm and remove it. Trim the end of the filament, reset the temperature to the standard and re-load the filament. This will sometimes pull out debris lodged in the nozzle.