Ok, in that case it should be fairly straight forward, though you have to decide whether you want pixel-perfect (slightly smaller screen area) or scaling (might be a bit fuzzy, but will work with most apps and games).
I am going to continue on the assumption that you want pixel-perfect (if not, we change later):
From command, experiment with something like:
nvidia-settings --assign 0/CurrentMetaMode="DFP-0: 1920x1080 { ViewPortOut=1880x1050+20+15 }"
The numbers are most likely not right, but let's see if we get close.
Let me know if this works, and if so, is the display still too big or too small... then we shall tweak.
Cheers!
CJ