There are a few reason why your jaw can hurt when chewing or talking.  If you been noticing jaw pain talk to your dentist about TMD temporal mandibular joint disorder.  Also jaw pain can be a sign that you are clenching or grinding your teeth.  Many people do this when stressed.  If you are having high stress currently, try to be more aware of this.

People can also grind or clench their teeth while sleeping. In this case it can be harder for you to know if that is what you are doing. However normally your jaw can be more sore in the morning when you first wake up.   Consult with your dentist.  Regardless of why your jaw is hurting your dentist will be able to determine the correct course of treatment.