I've had times when I thought I had burn in from using my PC (on a 42" panny plasma), but it turns out it was just short term.
Play TV for a couple of days without the PS3 on it at all.
If it completely goes away, you're good.
If not, there are videos you can play to level things out again.
Check you havent got the contrast at eye burning levels, that causes wear far quicker.