Hello, I suspect an active infection from the same tooth. Common conditions include: -inadequate apical seal -additional untreated canal -fracture of root I recommend taking an x-ray to evaluate the healing process. Antibiotic treatment may help the area to resolve. Amoxicilin is the typical antibiotic of choice. The history of the tooth and events concerning the need of the root canal would be helpful. A very resistant infection may require additional antibiotic treatment. Is this a recent root canal needing more time to heal? Did you take antibiotics and complete the medication as prescribed? You can have resistant infection that may be resolved with antibiotic treatment. The tooth would continued to be monitored at recall visits if it resp onded well and no other problems were diagnosed. What is the description of the bump? Is it filled with fluid and drains? I recommend rinsing the area with warm salt water and taking anti-inflammatory medications such as Tylenol or Motrin to help resolve the bump until you rturn to the dentist for further evaluation. You may consider an evaluation by a root canal specialist. Some secondary, non-resolving infections require a surgical root canal procedure called an apicoectomy. Thank you for your inquiry. I am available and glad to answer additional questions.