Just something you have to get used to, you can't just force yourself to forget about it or not be bothered by it. It's just a perfectionist mentality. Same as me I know at least 3 or 4 "friends" who has a dead pixel on their ipod touch and (or) beaten and scratched cell phone cases. I try and keep all my electronics in pristine condition and when something small like a scratch gets on them it really bugs me.
The more you try and forget about it the more you tend to think about it. Just put your PSP away for a few days or weeks and when you come back to it just look around at something else when your game is booting so you don't focus on it. Also a dark or black wallpaper really helps.
Or instead of that just accept that you have a dead pixel and let it at that.