I can't tell if it's an injury or what the problem is, but you do have problems.
Can you move it to a hospital tank?
If so, I would start with daily water changes. Since it is an open wound, I would also add antibiotics to the tank for 7-10 days. Erythromycin or sulfa would be my first two choices, but I don't know what is available to you there.
I too have this same hole on 3 of my yellow labs and 3 have died in the last couple days. It's behind their side fins on one side of their body. Some are acting very lathargic and one seems normal and happy. I've also lost an afra and a demasoni in the last couple days but they showed no symtoms before death. I'm stumped and started treating with metro since that's all i have at the moment. I changed 40% between the first and second treatment. All water parameters have been perfect. The tank has been established for about 2 yrs with only a bloat problem about a yr and a half ago. It was moved about 3 months ago. The yellow labs i've had for about 3 months as well. The only other changes i can think of is that I started using Cichlid Lake Salt about a month ago. Also is it alright to use regular aquarium salt with the Cichlid Lake Salt?
I've always used regular Aquarium Salt just for the benefits of the fish. After reading a lot on the forums I decided to start using "Cichlid Lake Salt" from Seachem just to add the trace elements that are natural to lake Malawi. I did as the directions said and only added the salt based on water i was replaceing. I don't really know if the holes correspond to me adding the salt. It's just that it's about the only think i've done different in the last month or so. Today one of the yellow labs seems much better, one about the same, and the rest of the tank seems to be in great shape. I've been dosing them with metro. Do you think I should continue with this treatment or use something else?
Yeah i'm trying to soak the food first and a few are at least mouthing the pellets. Should I not be using the Cichlid Lake Salt? Besides having bloat once a long time ago I've never had any other problems with my 2 aquariums. I just thought the fish might like it better but honestly i can't tell a difference. Also my PH out of the tap is around 7.8-8.0