I had the same problem. Sorry but, it's a hardware thing and the LCD panel needs to be replaced. Also, it gets worse over time, mine started off with one pixel wide and widened to 10-15 pixels in a couple of months.
If you are within warranty, great.
It not, you could order a new LCD and do it yourself. The repair service gave me a 700EUR quote for replacement, I just bought an LCD off of EBay for 200EUR and did it myself. Repair guides can be found on ifixit or powerbookmedic.com.
Good luck.