Your iPhone screen is comprised of hundreds of thousands of tiny pixels that render an image. Each pixel is made of three colored subpixels; red, green and blue. Normally these subpixels electronically cycle through the three colors depending on the displayed image, but if one get stuck in the “on” position, a solid-colored dot appears on your screen. Gentle pressure on the stuck pixel may fix it, but results are not guaranteed.
Make note of where the stuck pixel is on your iPhone screen. Use a dry erase marker or low-tack painter's tape to mark exactly where the stuck spot is. Repairing a stuck pixel requires precision.
Power down the phone. Place painter's tape over all openings, such as the headphone jack and USB connector.
Wrap a blunt-tipped object, such as a permanent marker cap, pen stylus or the edge of a pencil eraser, in a damp, soft cloth. Avoid fabrics that may scratch your screen. Don't dampen the cloth so much you risk water damage to your iPhone.
Apply pressure on the stuck pixel with the wrapped object. Apply gentle pressure on only the stuck pixel for 10 seconds.
Wipe up any remaining moisture on the iPhone's screen and power on the iPhone. Check for the stuck pixel. Repeat the procedure if the pixel is still stuck.
Try this pixel-saving technique at your own risk. If you cause more damage in your repair efforts, you may end up with more than just a single red pixel on your screen. Your warranty may not cover stuck or dead pixels, and you may either have to live with the screen problem or pay for repairs.
Work slowly, carefully and deliberately. Pressing too hard in too wide of an area can cause more damage to the stuck pixel or surrounding pixels.
If your iPhone is jailbroken, you can download and run the ScreenTest app available from Cydia. This program focuses on the stuck pixel and performs a color-changing cycle in an attempt to “unstick” it.