Hello and hope you are doing well.
Lymph are protective mechanisms of the body and they 'trap' the infecting source causing enlargement of lymph nodes. The infection can be from the draining skin or the organs. You could see if any of the draining areas have any evidence of infection, like tonsils, the skin, tooth abscess or an ear infection. Infections like tuberculosis can cause lymphadenopathy. It would be worthwhile to see if other lymph groups are enlarged namely, axilla and groin, these can be palpated. If persisting consult your doctor for an evaluation.
Hope this helped and do keep us posted.
Have you consulted with a physician yet?