IN the given OPG x ray film, the left lower third molar doesn't seem to be an impacted tooth. There is a deep filling in that tooth , pain may be due to that filling, or it can be due to impingement of the upper tooth to the tissues just beyond the lower third molar causing tissue inflammation and pressure on lower tooth.
Next Steps
consult with an endodontist first, if the left lower third molar cant be saved with root canal treatment ,then that tooth may need to be extracted.
Health Tips
if pain persist after extraction of that tooth , then upper wisdom tooth extraction may be also considered.