Hi. There can be several reasons for the swelling. 1. Gum infection around that area 2. Cavity in the involved tooth causing swelling 3. If the tooth is your wisdom tooth then it can be due to food accumulation around it due to improper cleaning Exact problem can be found only on proper examination. But for the time being you can use any kind of gum paint 3 times a day or do warm saline rinses 4 to 5 times a day. Both of these are temporary solutions. Proper treatment will be needed once cause is found.

If there is some foreign body thats lodged in your gum it will take sometime for gum swelling to come down . You can apply a gum astringent .