Trouble with hood hinge - need advice

[Guy Dudebro]

I took off the hood of my 67 c10 to paint it. Putting everything back together, bolted on the hinges. Placed the hood on the hinges, bolted three bolts from the hinge to the hood. But the fourth one must have lost its nut. See pics below.
So the hood won't close all the way. I have to set a cinder block on the back passenger side of the hood to make the weight enough on the hinge to shut.

I tried putting a rubber well nut up there but that didn't work. Is there a way to get inside the hood, take off the mounting where the hinge attaches to the hood, and put another speed nut in there?

Any help is appreciated.