call apple and get them fix the display , that what the warranty is for

but they will only replace the display if there are to many of them , they have guidelines what amount is acceptable
but you got so many working pixels ,so a few are acceptable on a lcd display from any manufacturer, thats the downside of LCD's
and you could face a replacement with even more so called dead pixels that you may already got, a reason why i never would buy a expensive lcd monitor , because it would make me angry having to live with even one dead pixel , as once you know its there you will always stare at it , on a cheep second hand monitor , i just dont bother and get another one, but most of my Mac's have a build in crt anyway ,and i have a couple old crt studio displays for the rest much more reliable and never will get dead pixels , god this modern technology is so advanced
but you got always a chance if one at apple has a good day and you get a replacement display , some even managed to get a replacement iMac with no dead pixels , but they can occur later