What can be done to treat this exposed piece of mandible bone? Is it even treatable at this point, or am I out of luck? (Photos)

I am 32 and I have no teeth. In 2002 my dad died and I, admittedly, grieved in the worst way possible. I used, and began a decade long addiction to, drugs and alcohol. Because of those poor choices, aspects of my health suffered, such as my teeth. Over the course of a few years I had them extracted, little by little. The last such extraction was 3 years ago, 14 teeth at once. This area, obviously, never fully healed. It is pretty sensitive and painful at times, feels like an exposed nerve.