my iPhone is show only white screen and black apple after erase on icloud
I am assuming your phone is not turning back on, if so then just do this.

Hold the Power Button (3 secs)

Continue holding the power button and also hold the home button (15 secs)

Release the power button while continuing to hold the home button (10 secs)

Your device should prompt with the "Connect to iTunes Screen"

From here just set up your iPhone as new or restore a previous back up.

Try this a few times just to make sure you did it right, however if this does not work then be sure to take it to the apple store.