No
I don't believe that that is fungal.
It is also unusual to see fungus in that area of the shell.
But if you are still concerned...Go to your area "Dollar Store", get a tube of Athletes foot cream and wipe some on the area.
It will quickly kill fungus...Yet do NO HARM if there isn't any.
To me, it looks like a superficial abrasion of some type of a mineral stain.
Athletes foot cream and a tube of general antibiotic ointment (Also for sale at the dollar store) Are great items for a tortoise first aid kit.
Could be a dried out area due to heat source (basking light)being too close. Usually that would be on the top of his shell not on the sides though unless your heat source is angled weird.
What's the texture? Looks like an abrasion to me as well. If it feels like he scraped his shell, that's probably what it is, and if so, it's not nearly deep enough to cause any concern, at least from those pictures.