thanks for asking your query
could be of multiple reasons like inflamation,infection,local irritant,trauma,food impaction
the best treatment for swollen gums is the removal of plaque and tartar
Practice good oral hygiene
. Brush your teeth twice a day and floss daily. Visit your dentist
regularly and ask for tips to improve your technique. Over enthusiastic brushing and flossing can do more harm than good, leading to swollen bleeding gums
Eat well. A well-balanced diet, including plenty of vitamin C and calcium, may reduce the likelihood of developing red swollen gums. And drinking plenty of water helps remove food particles from your teeth after a meal.
Avoid things that irritate the gums. Swollen sore gums may be aggravated by mouthwashes, alcohol and tobacco. Choose lukewarm or cool food and beverages instead of extremely hot ones that can be painful if you're nursing red swollen gums.
Relax. Stress isn't just bad for your overall health, it can also lead to swollen sore gums. Being stressed raises levels of the hormone cortisol, which leads to inflammation throughout the body -- even in your gum
hope this will help