Hi! Welcome to healthcaremagic. I read your query. As you mentioned you are having orthodontic treatment right now. The gum swelling after band placement is traumatic periodontitis. The band or the braces might be impinging in your gums leading to irritation and abscess. I suggest you visit your dentist and get adjustment of band and braces done in dat area. Also, dont pinch or squeeze the swelled area as it can cause infection further. Maintain good oral hygiene. You can use orthodontic brushes. Use mouthwash or warm saline rinses. Do rinses after eating or drinking. Massage gums with gum paint for increasing blood supply and soothing. Maintain good diet. And get oral prophylaxis done at regular intervals of 3-6 months. Hope the answer helps you. Thank you!