My guess would be that the PTFE tube in question has distorted. It is not really supposed to come out of the stainless steel heat dispersing tube.

I would warm it with a hot air gun gently until the PTFE tube comes out then pick out the plastic that is stuck in there with heat as much as you can then clean with Acetone or MEK. << vicious stuff is MEK be careful.

It does seem that there is a lot of evidence that sort of says that once a nozzle has started blocking it will continue to block and it's best just to replace it. Certainly on mine that was the case. For the cost of these parts it is best to consider them as consumables, chuck that one in a box marked "spares that may work" and buy a new nozzle and stainless tube.