kubuntu - Ubuntu fails to boot after updating nvidia drivers

I have a Dell XPS 15, and my computer runs Kubuntu 16.10. I recently updated my NVIDIA graphics driver (through the terminal), and while installing it asked me to "turn off Secure UEFI Boot", so I did, and rebooted my computer, and then the computer doesn't start. It gets stuck at a black and white terminal-like screen that says:

[6.036253] brcmf_c_preinit_dcmds: Firmware version = w10: Nov 10 2015 06:38:10 version 7.35.177.61 (r598657) FWID 01-ea662a8c
[6.074532] brcmf_cfg80211_reg_notifier: not a ISO3166 code (0x30 0x30)
[15.660363] brcmf_inetaddr_changed: fail to get arp ip table err:-23

and won't go any further. I am very new to Linux and need help on how to fix this; I have some important work on this computer that I would really like to keep.

I think you need to reinstall drivers from terminal. Reboot and select recovery mode in GRUB. Log in. Run

sudo ubuntu-drivers devices

It will list drivers that fit your card. Select a version and run

sudo apt purge nvidia*
sudo apt install nvidia-???

to install.