Hi.. Welcome to HEALTHCARE MAGIC.. I have gone through your query and can understand your concerns.. As per your complain due to physical injury caused by injury to the side of the face there seems to be inflammation of the soft tissues leading to swelling and difficulty in extending the jaw can be due to inflammation of the muscles while there can also be injury to the jaw joint also known as Temporomandibular joint leading to conditions like dislocation of articular disc that is a soft cushion between bony ends of joint, dislocation of lower jaw or there can also be hairline cracks in the condylar process of lower jaw leading to pain and inability to extend the jaw completely.. You should consult an Oral Surgeon and get evaluated and a full mouth x ray known as Orthopantomogram [OPG] can be advised to you to evaluated the exact cause of the problem and treatment cn be planned accordingly.. As of now you can take anti-inflammatory painkiller like Ibuprofen or Naproxen or Diclofenac potassium, muscle relaxants like Chlorzoxasone, do cool compresses over the swollen area,take a soft diet and avoid excessive mouth opening.. Hope this information helps.. Thanks and regards. Dr.Honey Nandwani Arora.