Hi and welcome to the forum
How long has the tank been set up for?
How often do you do water changes and how much water do you change?
Do you gravel clean the substrate when you do a water change?
How long have you had the gourami for?
Have you added anything to the tank in the last few weeks?
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The damage could be from the fish scratching itself on something or it could be a bacterial infection.
Dwarf gouramis (Trichogaster lalius) are regularly infected with the Iridovirus, which causes sores and wounds to appear on the body. There's no cure for the Iridovirus but if you treat secondary infections and keep the fish healthy, they sometimes recover.
Is the fish still eating well?
Try doing a 75% water change and gravel clean the substrate every day for a couple of weeks.
Make sure any new water is free of chlorine/ chloramine before it is added to the tank.
Monitor the wounds and if they get worse you will probably need to treat the fish with a broad spectrum fish medication. If you have a spare tank, it would be better to treat the fish in the spare tank.
You can add fish vitamins to their diet. If you can't get fish vitamins, you can use reptile or bird vitamins. If you use reptile or bird vitamins, only use it 6 days a week and do not use it on the 7th day. Fish vitamins can be used every day.
You can try adding juice from orange or purple foods like apricots, orange squash, carrots, blueberries or purple carrots. You add the juice to some fish food and let it soak for a minute before feeding the fish. Orange and blue/ purple foods have lots of anti-oxidants that can help boost the fish's immune system.