Severely Injured Goldfish Options

[Wahaj]

Even though I'm freaking out right now, I'm going to take my time to explain the situation from the beginning. So, I own a 55 gal tank which has 4 orandas in it - 2 black moors, 1 orange lion head oranda and 1 red cap oranda. I got my tank about a month ago and its probably still cycling. It currently only has an under-gravel filter installed in it. I have been doing partial water changes (about 75% - 80%) every week and I have been feeding them twice a day, with peas and live food once a week but I did take care not to over-feed.
The problem started about a week ago when my red cap oranda started swimming erratically and long light coloured threads possibly with air bubbles were hanging out from its anal area. I instantly knew that it was constipation and fed it peas. It got better the next day and even better the day after that so I stopped with the peas and came back to my usual pellets. After feeding soaked pellets till the day before yesterday, I saw when I woke up yesterday morning that the red cap was swimming upside down so I decided that I wasn't going to feed it for 3 days and then feed it peas for the next couple of days, change my pellet food and probably give it epsom salt baths today so I didn't feed it yesterday. When I woke up today morning, I found out that the red cap oranda had gotten stuck in the fake hollow drift wood imitation that I had in my tank (I've removed it now) probably made of clay (both of its ends are open with one end broader - broad enough for the goldfish to get in and the other end narrow enough for the goldfish to get stuck). I immediately tried to get it out but couldn't and in those attempts, I completely destroyed its tail fin. There was noway the fish was coming out because I had been trying for the past 10-15 minutes and couldn't get it out. In panic, I shook the decor so my the fish would come out and it did but it was SEVERELY INJURED! Now....ALL of its fins are in shreds! Its lying on its side on the bottom of the tank and it has a crazy big wound on one side of its body and a smaller wound on the other side. The wounds are all flesh and no scales. What should I do? Please help!
And sorry that my question got so long Also, I live in Pakistan so most products available in the US or Europe wont work for me. If possible, could you tell me about treatments (if any) that are general and not brand specific 'cause I wont be able to get those brands here in Pakistan. Thanks.