If bony healing has truly completed (confirmed by an xray of the area) then your only options are:
1) Guided tissue regeneration with bone grafting
2) Surgical crown lengthening
The option selected would depend on what the current gum and bone level is.
Bone grafting done as part of guided tissue regeneration can help fill in the bony defect (space) left behind by the wisdom tooth. In older adults (above 25 years old), good bony infill may not occur after surgery especially if the back (distal) surface of the 2nd molar has not been thoroughly cleaned out after the wisdom tooth has been removed. This is an appropriate option if the gum level after healing has receded to the ideal position (at the dentino-enamel junction, DEJ, of the tooth) or slightly below the DEJ after the surgery.
If the wisdom tooth was quite superficial or if the bony ridge behind the lower teeth (the ascending ramus) is very prominent, then some patients may heal with an excess of gum that may creep over the distal side of the 2nd molar.
Merely removing the excess gum (gingivectomy) tends to be only temporary, as the underlying bone level is high enough to support regrowth of the excess gum tissue. Surgical crown lengthening to reposition the bone and gum lower down the tooth would be more predictable.
Careful suturing (stitching) technique will also help to approximate the tissues correctly and promote healing in a way that prevents formation of a pocket.
