Actually most companies have what they call an accepted dead pixel policy (read the fine print on a lot of LCD screen manuals). Generally this isnt an issue on a big ole screen unless is smack bang center. On your smaller N900 screen I can see how this would be a royal pain. Contact Nokia - they may replace it - they may not. Often it depends on how fast you talk

My first N900 also had two hotpixels, one on the upper left corner (where the dashboard icon is) and another one about 2cm below the first one. They were annoying, especially when the background was black and the screen brightness was set to 3 or above.

I already sent it back to Nokia. Got another device, this one has two bright hotpixels in the screen center, one on the top border of the screen and one on the middle right boarder. That's a total of four hotpixels on the new device. Sent it back too.
In addition to that, the brightness got weaker from the left to right boarder, on bright background this was a problem.

This is really annoying, you are spending 600 €uros (the most expensive phone I ever ordered) on such a device and have to return it two times. Now I just hope that my third N900 will be okay. Maybe I was just lucky, but I have never had a single pixel error on my last three phones (E90, HTC Touch Pro and Touch Pro 2).
Even if there is a pixel policy, this is a small screen and you can notice errors like that much easier than let's say on my 24" screen. And for a 600 bucks flagship device this is something which simply should not happen.

You can check your device easily, just open up a pitch black picture (wallpaper) and view it in fullscreen, this is the easiest way to spot any pixel errors. Same goes by the way with viewing a plain white pictore, to spot dark pixels.

There were simple programs in the past that would cycle through colors in a rapid fashion and with some luck they could get stuck pixels unstuck. Maybe this is something that could be made for maemo, should be too difficult.

A pixel will not change size by massaging. Unless there were other dead/stuck pixels beside it, you're just experiencing a placebo effect. Reason why it doesn't change in size: the whole pixel essentially lights on or off, never "half-half."

You see, son, a dead pixel is a lot like a woman..