Usually when a patient reports this symptom they are experiencing an infection of their wisdom tooth. When the wisdom tooth is partially impacted, this is called a pericoronitis. If left untreated this infection can sometimes cause difficulty in swallowing and even spread to the neck area.
The treatment for the pericoronitis usually involves cleaning the area under the flap of gingiva that is covering the wisdom tooth, placing the patient on the appropriate antibiotic for 7-10 days and having them rinse often with warm salt water. I ask them to place table salt in a cup of water and microwave it until it is warm and rinse six times per day.
In the case of an impacted wisdom tooth which is fully covered by a flap of gingiva, often it is not possible to clean out the area, but if I am able , I irragate the area with saline solution and place the patient on antibiotics.
I see the patient again one week later and discuss whether removal of the wisdom tooth is advisable.