Reactive lymphoid hyperplasia: This is the most common cause of a tonsillar nodule, often resulting from a viral or bacterial infection leading to an increase in lymphoid tissue.

Tonsillolith (tonsil stone): A collection of debris, including dead cells, mucous, and bacteria, that can form in the crevices of the tonsils, presenting as a nodule.
Squamous papilloma: A benign growth caused by the human papillomavirus (HPV), which can appear as a nodule on the tonsil.
Fibroma: A benign tumor of fibrous tissue that can occur on the tonsil, presenting as a firm nodule.

Squamous cell carcinoma: Although less common, this malignant tumor can present as a nodule on the tonsil, especially in smokers or those with a history of HPV infection. Early detection is crucial for treatment.
Lymphoma: Both Hodgkin and non-Hodgkin lymphoma can initially present with a tonsillar nodule, making it critical to consider in the differential diagnosis to ensure timely intervention.

Kaposi's sarcoma: A rare malignant tumor associated with HIV infection, which can present as a nodule on the tonsil among other sites.
Granuloma: Rarely, a granuloma (a collection of immune cells attempting to wall off substances perceived as foreign) can form on the tonsil, presenting as a nodule, often in the context of specific infections like tuberculosis or sarcoidosis.
Amyloidosis: An extremely rare condition where abnormal proteins (amyloid) accumulate in various tissues, including the tonsils, potentially forming nodules.