I agree on FLTDI's advice, but I'm worried that's not your culprit. If rewiring the switch doesn't stop the flicker, keep checking other outlets and lights on that circuit until you find it. I had a light recently that flickered whenever a lamp on the same circuit was turned on. I dragged my feet on investigating, and a couple of days later, it went completely out. When I took down the light and looked at the wires, they had burned up. I was lucky the heat/fire stayed in the box.

Agree with others. Call the man.

In the meantime, a loss of power could mean you have a loose connection in what you worked on. Loose connections cause sparks. Sparks cause heat. Heat causes fire.

Feel the wire nuts for any heat. You may find your issue. Otherwise, I highly recommend leaving all related circuit breakers turned off.