mine was only noticable at night too. Its hardly a massive, end of the world, type problem. But feel free to take it in and they will replace it for you. I noticed dust got under the screen, which may have been from this hole.
well, i got my replacement today, and was rapt that it had no dead pixels. I jumped in a closet (somewhere dark) to check for the light, and it has the same problem, this time a bigger, brighter hole. What should i do?!?!