Is my Russian tortoise okay?? (with photo)

[N3aDIA]

Hi guys! I finally have a chance to ask for an advice about my tortoise...
I don't know what is going on with his shell... it's kind of cracking... i was not able to find some sources about what he is having right now.. Can anybody tell me what is going on ?

 

[Yvonne G]

It looks like an old injury. I was going to say "light burn" but there's also a big chunk taken out of the carapace right above the head. Light burn doesn't take out chunks. So I'm goin' with old dog chew. I can't be sure without seeing it in person, but that part behind the missing chunk sort of looks like the new keratin that grows under old, dead bone. Was that spot white before this?