Well, since it's a new fish that I am assuming was not quarantined it could be anything. Seeing how the skin looks more like an ulceration that sloughing I would lean towards a bacterial infection or a coral sting. You have some options: put the Jawfish in a QT and treat with antibiotics if it is an infection. 2 leave it in the main, feed well with vitamins and keep water clean in the event it is just a coral sting but be prepared to move it into a QT if it is an infection.
However, if it is a disease you will need to move all fish to a QT and treat.
How is the fish eating, breathing, swimming and overall behavior?