Their skin is very fragile, so with swimming around and everything, it's pretty common that their tails especially get caught occasionally. If it becomes a regular issue, you can go through your tank and try to get rid of/sand down edges.
By the way, it looks like you have a great example of a melanoid! Can't tell from this pic if it's an albino or a leucistic, but if it's a leucistic yours and one of mine are matching! Lol