Hello and welcome to the forum.

I should start out by saying I'm not a doctor and I have no medical qualifications.

I'm sorry to hear you've had this worrying issue for so long. Please be reassured that most lumps aren't cancer, and many lumps in the neck turn out to be swollen lymph glands fighting an infection, but no one can say for certain without tests. Although lymph glands normally settle down once the infection has gone, a tiny number do remain harmlessly swollen for a very long time.

You don't say when the nasendoscopy was cancelled.  There were many cancellations when Covid first struck, but hospitals are re-opening more departments and the situation may have changed.  It would probably be worthwhile going back to your GP to have a chat about what's available, even if you have to travel some distance.  Even if an ENT appointment isn't possible, your GP might still be able to arrange an ultrasound scan which could yield some useful results and might be able to identify the lump.