Without a vet all you can do is seperate the fish, manually put the jaw back in place, add some salt (1 tbsp/5g) or melafix to lesson chance of infection, and then hope it heals, while waiting use low bulk, high protein, soft foods like 1-2" pieces of nightcrawlers.
Watch for mouth fungus or bacterial infections and treat htem as some as there is a sign of infection.
Hopefully the bone will set and heal correctly, if it is just a dislocation it will heal quickly.