From what you say, about the options of either an extraction or root canal treatment a couple of years ago, and the symptoms that you now describe, the most likely diagnosis is a chronic apical abscess around the tooth. This means that the nerves within the tooth have necrosed ('died') and that you have a low-grade infection around the root apex. From time to time the pus that builds up around the root tip drains through a sinus in the side of the jaw. The fact that it is draining will account for it not normally being painful. If it did not drain you would most likely have an acute apical abscess with pain and swelling as the symptoms. Whilst it is not painful at present, you run the risk of this occuring by not having treatment. The most sensible option is to return to your dentist to confirm the diagnosis and then decide upon which treatment option would be best for you.
Hope this helps.