In the early years of treatment with imatinib I had quite a painful swollen node on the right side of the neck and my haematologist examined it and declared it not to be suspicious but said that it would take 18 months to disappear and he was absolutely spot on.
He said that neck issues are quite substantial within the general population and seeing my general doctor he said there could be up to any one of twelve reasons for a neck issue. There are up to seven different locations/types of lymph nodes around the neck and chin-under the chin there is a submandibular one and a submental triangle and these are related to the lip ,mouth,tongue and gums so perhaps you should double check that you dont have an infection in any of these areas.
I was told that it would be very unusual for this kind of swelling to be associated with metastasis or a secondary tumour or otherwise lymphoma.In addition I was told that if my bloods and PCR scores were satisfactory that it was unlikely to be CML related.
I would suggest, as Sandy said, check it out with a specialist (either haematologist or maxillo -facial) but in the meantime do try to maintain movement with some regular neck exercises (google these) and reconsider the type of pillow that you use at night .Medium term I was told that some ultrasound would determine if it was problematic or a biopsy in the form of a fine needle aspiration but normally that is only used where the swelling is quite large.
Regards
John