I hear a rubbing sand sound in my left ear when i open my jaw.....what could this be?

Temporomandibular: The temporal mandibular joint (TMJ) is located just in front of the ear and when there is irregular movement of this joint the jaw bone, one of bones of joint, can sublux from the TMJ socket, which invaginates the base of the skull. A common reason for irregular TMJ motion is spasm of one of the masseter muscles, which connects the jawbone to the skull, thereby effecting jaw closure.