My left jaw is very painful after wearing Invisalign. What could be happening?

I recently started Invisalign and my left-jaw started clicking after I switched to Tray 4. Then 2 days later, my left-side jaw started to hurt very badly, especially when I try to eat or open my mouth. Now (a few days later), the problem worsened and the orthodontist just told me to take Advil. I don't want to just take painkillers without knowing the cause. He said that it could be caused by teeth grinding . How is this related to Invisalign? Is there anything I can do besides taking Advil?

No doctor answers yet