Jaw locked shut on one side.?

Closed lock: Probably an issue referred to as a TMJ closed lock. This is not dangerous and usually is a result of inflammation resulting from chronic bruxism (tooth grinding) while you are asleep at night. It will likely resolve on it's own, but may require a visit to an oral surgeon. You'll want to consult with your dentist for splint therapy to avoid this in the future and to protect your joints and teeth.

Articular disc: Usually due to the articular disc moving out of the glenoid fossa and obstructing the mandibular condyle from rotating properly. You need to "recapture" the disc so that it moves back into its proper position.

See OFP specialist: TMJ syndrome may cause ear pain, ringing in the ears, jaw locking, and pain behind the ear. Proper diagnosis is the key to successful treatment. See Orofacial Pain expert for a consultation and treatment options.