I microphone needs only one input channel. Therefore you only need to record from that one input channel.
Create a MONO track in your DAW and set it to your microphone input channel. It will record only that one input channel.
When you play it back, the DAW will mix to both Left and Right "output" channels.
The only time you need to record two input channels to a "stereo" track is for audio sources that have a Left and Right output. Mixers, Keyboards, etc...