I need more pictures that are in focus and from different angles.
It looks like a physical injury but could be a bacterial infection. If the tank is well maintained and you have had the fish for a month or more, it's probably a physical injury.
Do a 75% water change and gravel clean the substrate every day for a week. This will dilute any disease organisms in the water and provide a cleaner environment for the fish to recover in.
Make sure any new water is free of chlorine/ chloramine before it's added to the tank.