Just take it back to the store, they offer a return policy anyway. I would say they will just replace it on the spot. If not, get a refund then go buy one again
I picked up my wife's iPhone the other day, and she has at least 30 stuck pixels on it! They're only really noticeable on a black screen. I told her to make an appointment to return it for a new one, but she'd rather keep it and not worry about the hassle. Women...