I think I was able to reproduce this, we may have accidentally let you set a mouse key as a key binding in the game. Just fixed that, in the next update we'll ensure this cannot happen anymore.
As for how to fix your situation... can you still use arrow keys and Enter to navigate through the menu? That way, navigate to Settings -> Controls -> check Keyboard and then select Set buttons P1 -> Reset to default. If this doesn't work, contact us directly and I'll think of a custom fix.