Tonsillitis: Given the patient's symptoms of pain in the left tonsil, palpable swollen hard lymph node in the superficial cervical region, and pain with swallowing, tonsillitis is a highly plausible diagnosis. The recent history of a family member (wife) having a staphylococcus infection could suggest a bacterial etiology, although viral causes are also common.

Peritonsillar Abscess: This condition is a complication of tonsillitis and could explain the severe pain and difficulty swallowing. The presence of a hard, swollen lymph node supports the possibility of an infectious process.
Lymphadenitis: Inflammation of the lymph nodes, which could be due to bacterial (including staphylococcus) or viral infections, is consistent with the patient's symptoms of a palpable, swollen lymph node and recent exposure to someone with a staphylococcus infection.
Oral Cancer: Although less likely given the patient's age and the acute presentation, the use of nicotine pouches increases the risk of oral cancers. A hard, swollen lymph node could be a sign of metastasis.

Lemierre's Syndrome: A rare but potentially life-threatening condition characterized by tonsillitis followed by cervical lymphadenitis and septicemia, typically due to Fusobacterium necrophorum. The patient's symptoms of tonsillar pain and cervical lymphadenopathy, along with the potential for severe infection, make this a critical diagnosis not to miss.
HIV Infection: Acute HIV infection can present with symptoms similar to mononucleosis, including sore throat and lymphadenopathy. Given the patient's age and potential for exposure, this diagnosis should be considered.
Tuberculosis (TB): Although less common in some regions, TB can cause cervical lymphadenopathy and should be considered, especially if the patient has been exposed or has risk factors for TB.

Kawasaki Disease: An acute febrile illness that predominantly affects children but can occur in adults, characterized by lymphadenopathy, among other symptoms. The absence of fever in this case makes it less likely.
Castleman Disease: A rare disorder that involves an overgrowth of cells in the body's lymph nodes, which could explain the lymphadenopathy. However, it typically presents with more systemic symptoms and is less likely given the acute infectious symptoms.
Sarcoidosis: A condition that can cause lymphadenopathy, among other symptoms, due to the growth of granulomas in various parts of the body. It is less likely given the acute presentation and infectious symptoms.