As there is tenderness, it could be an infection which is causing the asymmetrical enlargement of the
tonsil. Sometimes persistent enlargement of the
tonsil can sometimes be due to a lymphoma. It would be worthwhile to see if other lymph groups are enlarged namely, axilla and groin, these can be palpated, the others like those in the chest or abdomen may need a CT to detect their enlargement. Sometimes the tonsil may be removed for histopathological study.