Go have it checked out!! It may be something as small as an infection or it could be as bad as a cancer, You may need some antibiotics, Be safe and have it checked
My mother who has both Hodgkin's Disease and non-Hodgkin's Lymphoma first manifested the Hodgkin's Disease with a swollen lymph gland on the right side of her throat. Then, other symptoms appeared... a severe rash that turned into sores along with an uncontrollable itch all over her body; a persistent fever; drenching night sweats and unexplained weight loss.
Mind you, there can be different reasons for a swollen lymph gland. My mom's condition is just one explanation. But, it's not the only explanation as a swollen lymph gland can simply be a symptom of an infection. And, a persistent swollen lymph gland of... "a few months"... would suggest that your immune system is definitely reacting to something. What you need to find out is what that something is.
Like Valerie1954 said, "Go have it checked out." ... Please!