If your teeth are sore from grinding, it is likely due to the pressure and friction that is placed on your teeth when you grind them together.
When you grind your teeth, you are applying a significant amount of force on your teeth, which can cause the enamel (the hard, outer layer of your teeth) to wear down.
This can expose the sensitive layers of your teeth, leading to pain and sensitivity.
Additionally, grinding your teeth can cause the muscles in your jaw to become strained and sore.