It looks like your phone is on. But LCD is not turning on. Bong sound means it is on and charging.
Maybe 1 : everything is ok. Just reboot. How : remove the battery connector and LCD connector and reconnect both. Plug in to charger to see apple logo.
Maybe 2 : LCD cable damaged while power button fix. You need a new LCD.
Maybe 3 : some components on mainboard just next to LCD connector are damaged. It needs to be soldered under microscope.
Good luck ...