Technically, you have a stuck pixel (a dead pixel is one that won't light up). In rare cases, they do fix themselves, but that's highly unusual. There's no way to fix a bad pixel other than to replace the entire screen. If you got it from T-Mobile within the last 14 days, they may take it back.
I would call the carrier anyway. On a 17-inch LCD monitor with a 1280 x 1024 resolution, one bad pixel isn't worth complaining about. On a mobile device with a 240 x 160 resolution, a single bad pixel can be irritating. If the stuck pixel is especially bright, you may have two stuck pixels right beside each other.