My gums are swelling around one tooth. what can i do to reduce the swelling?

Treat the cause: When the cause of the swelling is determined, then it can be treated. Gum related? Dead nerve in the tooth? Periodontal defect? I know that you don't know, and it is impossible to diagnose over the internet. Why not give a local dentist a call and have that problem properly addressed.

See a dentist: If you notice swelling around one tooth, visit your dentist. Even if the gum abscess drains and the pain decreases, a visit to the dentist for complete treatment is important.

Not much: Swelling indicates infection, either of the tooth, the gum/bone that supports the tooth, or both. The infection requires professional care. Please call your Dentist. The sooner you address this the less the chance of complications.