Jaw has been stuck for three days now. how will the dentist get it unstuck?

Multiple ways: You should see a dentist, or perhaps an oral surgeon to evaluate the cause of your jaw being stuck. There are a few ways to unlock a jaw or get the joint to open more, but depends on the cause. Muscle relaxers, nsaids, physical therapy (tens), manual manipulation, or an oral appliance. They will be able to decide which treatment is best given your condition. Best of luck!

Pushing: If you are referring to a mandible dislocation, then the dr will apply downward pressure and guiding to usual position.