Had my lower last tooth removed 4 days ago cuz of decay probably have gum disease the spot now is black and yellowish and so is the cheeck next to it ?

Bruise likely: Most surgery involves bleeding and the more blood into the tissues the more it will discolor the tissue until removed by the body's normal functioning repair mechanism. If you are patient the tissue will usually return to normal color in a few more days.

Healing: If you have no bleeding swelling pain pus or bad taste/odor the extraction site will heal in a week or 10 days time.