3 week sudden onset locked jaw due to muscle spasm & joint inflamm no hx of tmjd/clicking/popping. what can cause this? desperate for help pain is bad

Uncertain : You need an evaluation There can be many reasons from muscle spasms to even conditions like tetanus

Locked jaw: Many possible reasons including slipped disc in the joint. Please see Dentist, Oral Surgeon, or ENT.

TMJ Disfunction : TMJ Disfunction can arise from several causes. These include: gum chewing, eating hard or very sticky foods, yawning too wide, trauma, and stress. First see an Oral Surgeon to rule out and/or reposition a slipped disk. Then see a physical therapist to treat the supporting muscled that are under spasm. Moist heat, softer foods and stree reduction can help as well.