A tiny piece of space debris is dangerous to the ship, as it may hit people, mechanisms, or fuel. But the damage to the hull itself would be negligible. It could simply be patched. The hull is the least of the concerns there. Solar sails typically don't contain people, mechanisms, or fuel that could be damaged.
A solar sail with a tiny hole in it could also be patched, whether with nanobots or with a regular robot and a patching kit. You could even send a human out to do it, although the human would then be effectively unprotected from more space debris.
For that matter, for some substances, the hole itself might be self-patching. Consider an opaque form of ice, say frozen mercury. The impact would liquefy the mercury, which might then close the hole after it. It would require some experimentation, but it seems like there should be some form of matter that would work like that. Mercury may not be that form of matter. It's just a possibility that came to mind.
Remember that at space temperatures, even things that are normally gases would be solid. Perhaps not hydrogen, but something should have a triple point and liquid cohesion that would work.
Beyond that, the hole would be tiny relative to the size of the sail. A big hole would add torque. But for the typical worry, the hole would be so tiny as to not be noticeable. The far greater cause of torque would be for the light source to hit unevenly. So if the sail can handle an imperfect light source, it should be able to handle tiny holes.
It would also be common to spin the ship to get an artificial gravity effect. This might offset the torque issue by constantly changing where the torque is.