Hello thanks for the quiery..
usually when you open the mouth too widely for a long time for dental procedures,, it might result in
tmj pain,,
Added to that you joint is also sore at the injection site??
so you need complete rest for the joint in terms of taking only soft food, hot and
cold fomentation alternatively,, and also muscle relaxants under the guidance of your treating doctor,,
plz consult a oral medicine specialist or tmj clinic if problem perists,, for a check up and treatment,, hope it helps,,take care,,