Cannot Boot or enter BIOS -- Help needed

I changed something in bios boot options. I can no longer see the dell logo on boot. I cannot enter BIOS to reset it (pressing f2 or f12 has no effect). my battery led is blinking twice amber and 7 times white. I can see a blinking cursor on the upper left corner of the screen.

I am not entirely sure what I changed, but I enabled legacy boot and some UEFI network boot option.

Any help is appreciated.