The bump on the gums can be because of sinus in relation to the decayed tooth or it can be gum abscess or can be a canker sore. If it is because of the decayed tooth then the tooth has to be either root canal treated or it has to be pulled out. If it is is because of the gum problem then the gum treatment has to be done.  The treatment may vary from deep cleaning to gum surgeries depending on the infection present and the amount of bone loss.  If it is a canker sore than it will heal on its own in 10-14 days .  There is no specific treatment for canker sores. You can do warm saline rinses for some relief.  Vitamin B supplements may facilitate the healing. Maintain a good oral hygiene.  If it persists beyond 10-14days, then consult your dentist. For more info on canker sores, you can refer to the following article… http://www.identalhub.com/article_canker-sore-234.aspx