What you may be seeing is what is known as sleeping pixels. Since it is a brand new machine, see if the return/exchange policy lets you get a replacement free, or if you might want an exchange under warranty. If they go away and don't bother actual images, I wouldn't worry about it. Sometimes if you very gently rub a sleeping pixel, it will go away quicker. But do not press too hard as that may damage the screen and void your warranty on it. So be careful!