4 months ago i had a molar extracted and developed a sequestration through a mandibular tori. the ulcer where the bone was exposed still hasn't healed?

Sequestration ulcer: It's possible there may still be a loose piece of bone, a fracture that hasn't healed, or an infection. You need to see an oral surgeon to have the area examined and evaluated.

Infection: This can be as a result of a bone infection which is not allowing the tissue to heal. Need to see a surgeon to evaluate and treat. Treatment may require antibiotics and possible surgery.