Hi,
You dont say how long ago you were dx with CML.
I had this same problem a few years into treatment for CML and was on imatinib 400 mg and was probably a similar situation to yours .I was examined by my hematologist who deemed it not suspicious and we did not go for a fine needle biopsy;he said that it would go away but it might take 12-18 months to disappear.It led to stiffness in the neck so did daily stretching exercises of the neck sitting upright in a chair-also I had a good and well qualified physio who did neck massage and stretching exercises for me.Before you let some one loose on your neck please ensure that they are fully trained.
My condition gradually improved over 12 months and by 18 months had gone.I was told that if there was any additional swelling around the neck to report but otherwise it would be highly unlikely to be an indication of lymphoma etc.Your biopsy result will hopefully put your mind at rest.
I never did get a full explanation of why my lymph node was swollen but some suggestions were that this might be the interaction between the CML condition and the treatment or that the body was reacting to an infection of some kind .So as long as you are happy with your PCR (below 0.1) and also that your lymphocytes score and your neutrophils are not too out of range that would be another re assurance.If you know your scores you could compute your own NLR (neutrophils /lymphocytes ratio) which ideally should be between 1 and 3 for a healthy person -if it was highly elevated it would indicate inflammation and an infection perhaps but not necessarily any other secondary cancer.Look it up on Google
You will of course have checked whether the underarm and groin nodes might be swollen as well?
I am not qualified to comment on the possible effect of the vaccine ( look at the product literature for J and J /side effects) but recently my specialist commented that even those who might have had a mild form of Covid or have been even asymptomatic might have long Covid effects.In his words Covid can do all sorts of things to you.
My situation was long ago so very pre Covid but I trust the above is useful to you.
Regards
John