It sounds like you want to have a physical push button that can be use to toggle the state of your relay, as well as a Blynk widget switch that can be use to activate/deactivate your relay. I assume that you want the Blynk app to be updated when the physical button is used?
If that’s the case then there is a sketch available in the sketch Builder examples:
Your problem is that the ESP-01 has a limited number of GPIOs. The example is written for a full-sized ESP8266 board, so uses a physical LED. The ESP-01 doesn’t have enough GPIO pins to do this (unless you sacrifice the serial communications, which I wouldn’t recommend).
Be careful when using GPIO0, as connecting it to a relay or switch that pulls it LOW at boot will prevent the board from booting. It depends if your relay is active HIGH or active LOW as to which pin is best to use for the relay.
More info on ESP8266 pins here:
Pete.