Sorry. I'm having a hard time imagining the exact spot. How are you feeling this hardness? With your tongue or finger? If its hardness and its pretty sturdy, it may be just your jawbone although I don't want to imply you don't know your own jawbone from something else. If it feels loose or moveable, it may be a broken piece of your jaw or tooth remaining in the socket. The gums will normally push out small pieces over a period of time. If it doesn't hurt or your symptoms improve, I would leave it alone and bring it up to your dentist next time. If it worsens, go see your dentist immediately.
hi this area is on the outside of the mandible- not under tongue. I guess buccal side?? about 1.5cm from gum line.