Lymph node swelling can be caused by infections, cancers and inflammatory diseases.
By far the most common cause is infection. Infection from the surrounding areas that drain into the lymph nodes such as the legs, abdomen, groin area can lead to the swelling of the lymph node. If there is recurrent swelling, these areas should be examined to exclude a persistent source of infection.
Often a course of antibiotics may be given to see if the lymph node swelling settles.
If the lymph node is persistent, you should see your doctor to get this assessed. Less commonly, but not be missed, are cancers like lymphoma which often present with lymph node swelling. Your doctor can advise you further on the need for further investigations or treatment.