Set your shadow Minimum bias on the light's Property Tab to 0.10000000 or less and you'll be fine. that makes the shadows minimum rendering small enough to fit inside the nostril, I guess.

I cannot save the world. Only my little piece of it. If we all act together, we can save the world.--Nelson Mandela
An  inconsistent hobgoblin is the fool of little minds
Taking "Just do it" to a whole new level!