Could my extreme jaw muscle tightness be from an allergy shot i got a couple days earlier? it has been a few days and still not calmed down yet.

Unlikely: The most common adverse reactions to allergy injections typically occur at the site of the injection and within 30 minutes. This usually includes itching, redness and mild swelling. Uncommonly a more significant allergic reaction can occur such as asthma or generalized itching. Symptoms localized to the jaw with muscle tightness would not be expected. Other causes should be sought.