Search for a dentist in your vicinity using Practo and try to make a visit as soon as possible because it seems like a traumatic injury which has not healed till now and might require other interventions. The best treatment options can be evaluated after a proper clinical examination only. Alternatively you can post a good quality clinical photograph on Practo for an online consultation with a specialist. Roughly speaking, you might be suffering from a mucocele which will require surgical removal but this is a tentative diagnosis going by a verbal description. Regards.