cut on head

So I went to feed Caroline and found 2 huge scratches on her gills! Please help I don't know what they are from! I attached 2 pictures, one of Caroline and one of her tank in case there is something in it that scratched her.

Housing What size is your tank? 3 gallons What temperature is your tank? 80 Fahrenheit Does your tank have a filter? Yes, one that came with the tank Does your tank have an air stone or other type of aeration? I am not sure what that is so I am guessing no. Is your tank heated? Yes What tank...