TMJ pain on one side while opening mouth can be due to various causes such as stress,biting on hard foodstuff,yawning excessive mouth opening and for long hours of mouth opening engaging in chewing talking. However since it is not accompanied by clicking and ringing in ear it is mild.
Next Steps
it is best to consult an Oral Maxillofacial Surgeon to prevent further complication and to treat the issue with therapy and to cure it completely without surgery.
Health Tips
lifestyle modification getting adequate sleep can help.