Wipe the screen very well with lint free cloth, are the dots still present? If yes, Restore the iPhone with iTunes on computer. Are the dots still there? If yes, make Genius reservation and take iPhone to Apple for resolution under Warranty.
They should have one in Stock, but you never know. Call your Apple Store and tell them you have an iPhone 5 color and GB, and that you most likely will need a replacement, do they have any in Stock. If yes, go in, if not ask for advice on how to handle your problem.