Do you need to use a resistor in order to use a push button?
No, connect the button to the pin and to ground and then use INPUTPULLUP. Look it up
"Do you need to use a resistor in order to use a push button?"
yes, but not allways an external resistor :
if you connect the button between "+Vcc" and input, then you need an external pull-down resistor
if you connect the button between input and "0V" , then you can use the internal pull-up resistor when you set up this input in the sketch
in both cases, the resistor is there to avoid the input (high impedance) from being in an undefined state (floating) when the button is not pressed. In the 1st case, the input is LOW if button is not pressed, an in the 2nd case, it is a HIGH if not pressed