If the problem is persistent and he is getting recurrent they infections its better to opt for surgery I.e tonsillectomy...Drink plenty of water,eat soft foods like cooked cereal, mashed potatoes, soft fruits, yogurt and soft-cooked eggs...give adequate rest to your body..Avoid spicy foods or acidic foods. Gargle with warm salt water. gargling several times a day can help relieve throat pain...Consult nearest ent specialist they will do the needful.