hi, thank you for your query. One of the reasons for development of lockjaw is because the muscles in the jaw become worn and exhausted from both tissue swelling and weakness; as a result your muscles can’t open your mouth all the way resulting in this disorder. high blood pressure usually doesnt cause lock jaw.it is associated with other systemic disorders. for immediate relief you can use warm wash cloth over the mouth may help relax the muscles and allow the mouth to open more fully. Rest and fluids are other important factors. thank you wishing you good health