Question about O2 sensors

After installing new Magnaflow catted X and cat-back, I broke one of the O2 sensors, so went to Autozone and purchased a new Bosch unit (#13127). Installed the new one on the drivers side, old one on the passengers side. Now I have the dreaded check engine light on - haven't pulled codes yet, but my initial question is, is it possible that only replacing one of the sensors has caused it to throw a code? Any help appreciated! Thanks!

Matt

I'll try disconnecting the battery. It's kind of a weird deal - the CE light doesn't come on right when the engine is started. It comes on about three or four minutes after driving. I'll have to pull the codes.... thanks for the advice.

Matt