When changing the light bulb connected to Dimmer Switch, it's important to pull out the Air Gap Switch prior to changing the bulb. Pulling out the Air Gap Switch cuts power to the socket/dimmer so you don’t expose yourself to the risk of electric shock while replacing the bulb.
The Air Gap Switch is #7 on the diagram below, pull the Air Gap Switch out towards you. The LED night light on Dimmer Switch will turn off. Test the power by turning Dimmer Switch on and off, the light should not turn on, you can now replace the bulb.
Once you've replaced the bulb, push the Air Gap Switch back in, the LED night light will turn back on. Test the power by turning Dimmer Switch on and off, the light should now turn on and off as normal.