If there is bone exposed, you may need to go back to your dentist. Sometimes it may be a piece of bone called a bony spicule that is pushing out of the gum. These spicules are small pieces of bones left in the socket unintentionally after an extraction and the body naturally responds to these pieces by pushing them out. It sounds like they went back in again to remove it so there maybe a few pieces of left they might have missed. If there's no severe pain, I would allow it to heal and monitor the situation. If it worsens, definitely go back. The gums will heal and cover up the hole. It may take several weeks to months though. Until then, don't play with it with your tongue as that reaggravates the site.
well insoy after the extraction did u play with the blood clott with ur tongue? did u follow post operative procedures? cuz what u have maybe something called dry socket...u shouldn't leave it that way and go see ur doctor again