Yvonne G said:It looks like the scute is going to fall off. This is probably because of an underlying infection. You should take the tortoise to a vet and find out what kind of infection is under there and get it treated before it affects the rest of the bone/shell. There's nothing you can do to make that one scute stay in place, but you can prevent it from spreading.
In the mean time, buy some Betadyne and mix it appx. half and half with water and try to get as much as you can under that part of the shell - between the keratin and the bone. Don't do this more than once, as the Betadyne inhibits the growth of new cells.