update manger -> booting stops at login tty1 shell

[gasior.tt]

Hello, I am casual ubuntu user and don't know how to tackle this problem.

I had on my PC installed xorg/edgers nvidia drivers some time ago. And recently, I ran update manager which updated the kernel. Now after reboot, GUI doesn't start. Instead I login to the login tty1 shell.
So I guess the kernel update messed up with my nvidia driver
command:

sudo service lightdm start

gives:

start: Job failed to start

what to do?
thanks in advance!