Thanks mate, i'll add some forest bark later with coco coirI wouldn't be too worried about that white spot for now from what I can see here it could possibly be a part of scale that has been removed from rubbing or anything along those lines. The enclosure looks very artificial you may want to add some substrate and some proper hides for long term health.
That's nothing to worry. Probably some old skin starting to shed. Leave it well alone. It will look tattier than that at times but the old skin will rub off naturally as your tort goes about its business