Looks like a swollen third eyelid to me. Peter had an eye infection last year. I was told by the vet that one sided problems are way more likely to be due to scratches or other irritants. Problem with the liver or whatnot mostly show up in both eyes.
At my grandparent's apartment I once saw a tortoise almost falling down a 9 storey drop. We managed to get the owners alerted just in time. She had already managed to get one leg over a shallow ledge going around the balcony. Don't risk it.
In this case they have already met, but if you ever get another tortoise the newcomer needs to be quarantined for a several months at least (6+) to minimize the risk of introducing diseases to your other tortoises.
Appenzeller Sennenhund and Entlebucher are both cool dogs, and I am not just saying that because they are compatriots. :D
You can also use the Appenzeller to pulla cart if you want to.
Both can be bit wary of strangers, but you were looking for a dog that protects you as well.
Could ground up snail shells and or egg shells work as an akternative? Though I think I read somewhere that the calcium in egg shells is mostly bound in a form which the tortoises can't absorb...
http://voices.nationalgeographic.com/2014/08/19/female-turtles-talk-to-their-hatchlings-scientists-discover/
And
http://www.independent.co.uk/news/science/amazonian-turtle-mothers-heard-talking-to-hatchlings-to-get-them-into-the-water-9675739.html
My tortoise tries to bite when he sees fingers in front of his face. I use that to check the inside of his mouth and sometimes even to get him to eat new things. The moment he tries to bite me I put a leaf of the good stuff into his mouth. Sometimes he then starts eating all of it, even the...