Radiated tortoises don't have perfectly smooth shells. It's a natural part of their physiology. As long as you're not doing anything wrong don't worry about it.
My leopard tort has that to.. he went on a huge growth spert(from 419 grm to 700 in 3 months) so some of the new growth is raised a bit but i dnt see a prob with it as i know he is way heathier now. i would not worry just new different growth