A proper clinical examination by a dentist, preferably an oral surgeon, will be the first step towards evaluation of the condition. An x-ray called as OPG will be required to assess the bone and the root status. From the description that you are mentioned, it would be suggested that the offending tooth will require extraction. Try not to delay this treatment because medications will only provide temporary relief. You can search for a dentist in your vicinity using Practo. Regards.