Does anyone know what this red mark, possibly sore? On my cory catfish is?

I recently found white worms in my tank, I cannot get rid of them, so I started treating my tank with salt and water changes to no avail. I found my Cory cat with this on his side last night, does anyone know what it could be from?

can we get a picture of the side of the fish?

The white worms normally found in the gravel are found in most aquariums and live on uneaten food. If you do a 75% water change and gravel clean the substrate every day for a week or two, they go back into the gravel. They are harmless and do not need to be treated.

Ammonia levels read zero

I need a picture of the fish taken from its side, not its front.

It was difficult getting a good picture