Ubuntu wont load on startup

This happened after i locked out my pc (like sleep mode but doesn't sleep, it just locks the screen asking for a password) and leaved it for a couple of hours on. When i returned i rebooted it because i couldn't even write the password in the box in order to unlock the screen and this happened. It stays like this and does nothing, i could wait hours and expect nothing to happen. How can i fix this? Thank you