|If your PC plugs directly into the wall then you have no surge protector. If the PC plugs into somthing like a power strip and that then plugs into the wall then you probably have a surge protector. You can probably reset the surge protector if it tripped. If not, get another one.|
If you don't have a surge protector or you reset it or it didn't blow then AC power should be gettnig to your PC. In that case, if the PC is dead then almost certainly the power supply is blown. The bang was likely a capacitor blowing up. That by itself could have caused the PSU to fail or it may have blown the PSU fuse too.
When a power supply goes out it can take the motherboard with it. But the first thing to do is replace the power supply. If it powers up OK after that then consider yourself lucky.
Or it may seem to power up but nothing will show on the screen. That likely means the motherboard is bad.
The above is the most likely scenario. But it's not 100%. So if you have a known working power supply lying around the house you might want to try it before you go out and spend a bunch of money on a new one.