Many users will think the problem is that their mic is "not in stereo" as they only hear it on one side, however it actually the opposite! The problem is that you have chosen Stereo Input, when you want Mono, as you are only using one mic.
In your recording software there will be an Input selection, to choose what is recorded, such as Input 1, or Inputs 1-2.
If your track is set to a Stereo Input, like Inputs 1-2, it is assuming you are doing a Stereo mic setup, using two microphones, placing Input 1 on the Left and Input 2 on the right.
Thus when you only have one input, recording in stereo, you get this issue, audio only on one side.
To correct, be sure the Input to your track is set to Mono and your input number, such as Input 1, or whichever you are using.
This will correctly place the Input in the center of the stereo output, so it plays to both sides.
The example below is shown in Logic, but applies to other recording software too: