Depends on how severe it is and how long it's been present. There are basically a couple things you can try:
1) Watch different programming for a while. This is most easily done with a non-letterboxed DVD, since you don't have to worry about channel logos.
2) Make a computer image that's the inverse of your burn-in pattern and run that for a while.
How visible is the burn-in? If you can only see it with a solid background like a white screen, you have a good chance of being able to fix it. If you can see it on normal programming, you might be SOL...