Possible. Regular forces the ECU to retard timing to avoid detonation, thus probably upsetting the fuel maps and not burning the fuel optimally. As a result, more unburned gases go down the exhaust, and the O2 sensor picks them up. That would cause the O2 sensor to register either a voltage spike or drop, depending on the gases in question, and in turn the CEL would come on.
It won't kill your car, if you can clear the code, do so. Get the tank as close to empty as you can, and then fill with 91 and the light shouldn't come back on. If it does, the o2 sensor might've been overloaded and broke, although that is extremely rare.