Why was your finger in there in the first place? hmm...
Luckily this is an easily replaceable part. Instructions to remove and install a focusing screen in your camera is here:
http://www.focusingscreen.com/work/a350en.htm Sorry english in there sucks but it is still understandable.
If you are ok with changing it with a third party one, it will cost $50-100 depending on the one you choose.
http://www.focusingscreen.com/index.php?cPath=26_86
These focusing screens are different from the original one from Sony in that they have special guides in there to help you with manual focusing. See this page to understand how it works
http://www.focusingscreen.com/privacy.php.
In my old D40x, I took out my old focusing screen and put in one of these. Works wonders for manual focusing. And yes, I did it myself.