It would depend some on if your chain was the right length in the first place, but I'd say check if, and if you don't know how, look here: http://www.parktool.com/repair/readhowto.asp?id=26 (or any of a zillion sights on how to do this).

Probably you'll need to adjust it, you *should* need to adjust it if you changed your chain ring size, but if you're un sure, I don't want to assume that it was correct in the first place.