The following are some of the possibilities: 1. a periapical abscess of the tooth accompanied by a maxillofacial infection, which requires oral anti-inflammatory medication or intravenous fluids, the routine use of drugs such as cephalosporin or erythromycin, and usually requires treatment of the tooth and root canal treatment. 2. a swollen and painful side of the cheek may also be due to an infection of the maxillofacial space caused by an erupting abscess of the wisdom tooth. If the pain and swelling in the mouth is severe, the abscess can be incised, and it is usually recommended to remove the wisdom tooth at a later date after the inflammation has subsided. 3. The swelling and pain on one side of the cheek may be caused by the parotid gland, and it is recommended to take an ultrasound to confirm the diagnosis. If there is a stone in the parotid duct or a tumor in the parotid gland, surgery should be performed in a timely manner. 4. Swelling and pain on one side of the cheek may also be caused by temporomandibular joint disease, and a film should be taken to confirm the diagnosis, and if there is a problem with the temporomandibular joint or a fracture or bone fracture, the patient should go to oral and maxillofacial surgery or temporomandibular joint disease department for timely treatment.