PulsarWinds

Help, I have a UM2, now a UM2+ thanks to the Ultimaker upgrade kit. Still relatively new to the kit (borrowed from work during lock down. Have been using 0.4mm nozzle okay with PTA and switched to Filamentive rPETG to do the Prusa RC3 shields. Okay for a few days but now I (think I have a clogged nozzle): - slow / thin extrusion, cannot lay down enough material. I have tried to push material though and no luck and even switch back to PLA but that now cannot go through the nozzle. I do not have a fine enough needle to try to fix it so I tried to change the nozzle. - Nozzle will loosen okay but it does not come down very far and will not undone with spanner, socket attachment or pliers. - I'm doing this hot so material sticking should not be a problem. What do you suggest (whilst I order thin needles on Amazon)? - I wonder if I have somehow stripped the threads ( but should still come off) Richard