Hi, offhand there's not too much to point to lymphoma at this time. Although nodes usually go back down on their own after a while, sometimes they don't - for non-cancerous reasons such as a buildup of internal scar tissue, or an ongoing "immune activation".
My guess as of now is that there is some sort of immune reaction going on, which is causing all of your symptoms because immune cells produce powerful biochemicals. That especially applies to bad fatigue. But you shouldn't just forget about it without finding out the real cause, right?
Did you happen to have something like a very bad cold before all these symptoms started? Insect bite? Any fevers? Do you have a family history of unusual immune system conditions?
Can you post the sono report and the CT report of the neck? There might be a clue in there, that can possibly justify a biopsy.
Can you take a look at this diagram:
https://radiopaedia.org/cases/lymph-node-levels
and tell me what area (called a 'level') the suspected node is at?