P0420 2006 Prius questions

I recently ran my car out of gas about 25 miles away from the used car dealer where i bought it. I wasnt aware of the guess gauge on these vehicles. I was on two bars and couldn't figure out why it wouldnt go so i tried starting it several times until it quit trying. after reading forums realized it was out of gas and computer needed reset. after getting gas and reseting computer it ran great. on the way home though the cel light came on again once i got home checked it and it was a p0420, im wondering if i may have fouled the front o2 sensor by running it out of gas. Any input would be great before i just start throwing parts at the thing thank you in advance​