Hi!
Swollen lymph nodes in neck can be due to injury near the gland or when a tumor or infection occurs in the mouth, head, or neck. An infection or tumor in the areas of the lungs, breasts, neck, or abdomen will cause enlarged lymph nodes below the collarbone.
I don't wanna sound negative, but I must note that swollen but painless lymph nodes that are occurring in the neck(upper part of the body) are the most common sign of Hodgkin's lymphoma. Are you having some other symptoms?
Do you have a low-grade fever? Are you experiencing night sweats? Do you think you've lost weight purposelessly? Do you have constant fatigue? Do you find your skin terrible itchy?
Best wishes!
Marija