Contact your doctor. There are a variety of infections and inflammatory disorders than may be responsible for your symptoms. A detailed evaluation will likely be necessary.
You have generalized lymphadenopathy that has not been explained thus far. Since you don't describe other symptoms, this is likely a temporary reaction to a viral infection and the lymph node swelling should go away over the next seven to ten days. If it does not completely go away, call your doctor to arrange an evaluation.
If the lymph node swelling has already been there for three weeks or more, don't wait, contact your doctor's office today.