If he is not moving and not eating the area has probably become infected. That is the problem with injuries such as these- they can easily get secondary bacteria and turn septic. I would treat with kanamycin- active ingredient in Seachem Kanaplex. You will need to change at least 25-50% water before each dose to keep the tank low in organics so that the medication isn't offset by organics in water.
I've literally just checked on the tank and tested the water. 0 ammonia, 0 nitrite and 5 nitrate... His condition seems to be getting worse too. The wide stuff on his dorsal fin is spreading. I dont think that the water is infected because the other fish are all pretty well. I've removed him from the tank and put him in a massive bowl and added some prime.
What do I do next??!