Hi and welcome to the forum
The fish has a bruised nose from swimming into objects. The best thing to do is a 75% water change and gravel clean the substrate every day for a week. This dilutes any nutrients and disease organisms in the water and gives the fish the best chance to heal without medications.
Make sure any new water is free of chlorine/ chloramine before it is added to the tank.
Monitor the nose over the next week and if it develops fungus (goes white and fluffy), or develops a bacterial infection (goes red and inflamed), post another picture and we can talk about chemical medications. However, most fish will recover without any chemicals as long as the tank is clean and the water is in good condition. Basically, water change, water change, water change.
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Fish can panic for a number of reasons. Poor water quality (ammonia, nitrite or high nitrate levels). Improper pH. If someone bumps the tank. If the tank is in a quiet room where nobody goes they will become shy and panic more.
Check your water quality for ammonia, nitrite, nitrate & pH. Do a 75% water change any day you have an ammonia or nitrite reading above 0, and any time you have a nitrate reading above 20ppm.
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Stress from tank lights coming on when the room is dark can be an issue. Fish don't have eyelids and don't tolerate going from complete dark to bright light (or vice versa) instantly.
In the morning open the curtains or turn the room light on at least 30 minutes (or more) before turning the tank light on. This will reduce the stress on the fish and they won't go from a dark tank to a bright tank instantly.
At night turn the room light on and then turn the tank light off. Wait at least 30 minutes (or more) before turning the room light out. This allows the fish to settle down for the night instead of going from a brightly lit tank to complete darkness instantly.
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If fish are in a quiet room, hang a mobile in the room and have a small fan running. Tie some ribbon/ streamers (about 12 inches long) to the front of the fan and have the fan on oscillate so it moves left to right and back. The streamers and mobile moving about will help the fish get use to movement around them.
You can have a small television on in the room, no sound needed. The flashing light and movement on the screen can help fish get use to things moving in the room.
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Make sure you have a picture on the back of the tank. You can buy aquarium backings or make one from coloured card, newspaper, plastic bin liner, or anything else. Just sticky tape it to the outside of the tank on the back.
Make sure you have driftwood in the tank for the pleco to eat. they need it to help with digestion.
If you don't get any algae growing on the glass,s increase the lighting time and try to encourage algae to grow for the pleco to eat.
If you put some plastic ornaments outside in a bucket of water and add a small amount of liquid plant fertiliser (for normal garden plants), the water will go green and soupy and the ornaments will get algae growing on them. You can take those ornaments and put them in the tank for the fish to graze on. When they are free of algae, swap them for another one in the bucket.
Try to use smooth plastic objects for culturing algae on.
