First get an offline appointment and get it diagnosed properly for the cause behind the swelling. It may either be due to unerupted 3rd molar tooth with pericoronitis or impingement by opposing tooth. If there is pus at the site, that may aggrevate with warm saline rinse, so don't start with that immediately. Do not start any antibiotics by yourself.
Next Steps
Get a clinical visit done.
Health Tips
Applying heat in infection may cause space infection!! So, don't do it unless it's diagnosed and advised.