El Capitan won't boot after HDD repair

[eltong]

After forcely shutting down El Capitan as it was stuck, it wouldn't boot.

Booting in verbose mode I noticed that there was a HDD problem, so I repaired it with DiskWarrior.
After repairing, it won't boot. It gives some SoundAssertion error, followed by some Bluetooth error, and next again some SoundAssertion error. Then the screen clears up and only a small white rectangle shows at top left of the screen. That's where it stucks...

When booting in gui mode, it stucks at a loading icon (looks like this)

I'm not sure what I need to do.

Any help is appreciated!

 

[eltong]

After searching some more, I realized that it could be a graphics problem. However I don't know what to do. I'd want to avoid reinstall.