Hard to say; it looks mechanical more than anything... wind rubbing, lawnmower, etc. Without knowing the history, as in where you live, indoor or outdoor, what variety, etc. a guess is just a guess. Here's a pretty good link to UC citrus scarring that might help

Here is a link that might be useful: UC guide to citrus scarring.

I agree with John, especially the fruit on the left. That looks like wind scratching on the skin surface. The fruit on the right could have been pressed up against another fruit or branch, and could have had some water trapped against the surface, or had some rubbing against the branch. Not to worry.

Patty S.