It should recover - keep it moist and don't do it again! Its always best not to use the shortest cut in any case- better to mow more frequently. If its very short and then there's no rain for a while it will all go brown and take a while to recover. Grass is a plant after all and it needs some leaf before it can photosynthesize.

A newly laid lawn will be more sensitive than an established one anyway until its roots have grown down into the soil.