It is suitable for the case that the filament head can be seen in the pipe when it is clogged.
Observe that there is a filament head in the pipe, and first heat the nozzle to the extrusion temperature.
Use cutting pliers to pull out the deformed filament from the pipe.
Restore the extruder.
If the above Method One is not helpful (e.g. Fail to find the filament head in the pipe), you can replace nozzle directly by the following steps.
Heat the nozzle to the filament extrusion temperature.
Heat the tip of the needle.
Slowly pull out the needle after cooling to take out the jammed filament in the pipe.
Restore the extruder