Symptoms: The plastic is stuck inside my hot end and i cannot pull or push it out. I have a full metal hot end (E3D or AllInOne)
Did you shut down the printer while the hot end temperature was above 80°C?
Is the fan cooling the heat sink of the hot end is on and properly cooling the heat sink?
Solutions: On both of this cases, if you have a full metal hot end, the plastic might have expanded inside the hot end itself. In some cases, the plastic may also have expanded so that the input of the hot end is full of expanded plastic.
In that case you will need to heat up your hot end again and remove every part while the hot end is still hot. The plastic will melt at least on the bottom side and you will be able to remove the nozzle and pull out most of the plastic from this side.
If the plastic has expanded into the heatsink, you will need to heat up the heat sink enough so that the plastic will melt and you can pull it out of it! You can also use a small drill bit (1 or 2mm diameter), and drill a hole in the center of the filament. If you wait a few seconds, the friction of the drill bit inside the plastic will soften it and might also melt it so that you can pull it out with the drill bit.
Take your time as this operation can often take 1 hour or so. In this case, time is your ally, rushing will cause you troubles and you may damage the hot end.
Sometimes it could take me the full evening to be able to fully clean up my hot end from all the plastic!