Today my jaw made a loud poping sound accompanied by pain in jaw when I opened my mouth what could have caused this?

Joint displacement. This is not the same as a dislocation or subluxation but is a derangement of the disc of cartilage that is inside the joint and acts as a cushion between the bones. See your dentist to have the joint examined as well as to evaluate the way your teeth are arranged and fit together (your "bite"). Very likely you will need s "cat scan" or 3 dimensional image to accurately diagnose.
Dislocated. You have may dislocated your jaw if the pain has not gone away. The jaw a joint where 1 of the bones may pop out of place. It may pop back in itself when you open your mouth and the pain will go away (may still be a little sore but not painful). If your jaw will not stop hurting, see your doctor or dentist and they can put it back in place for you to relieve the pain.