Sripped Hood hinge captured nut?

[purple gas]

So drivers side rear nut that the hood hinge bolt goes into is stipped.
Somewhere along the way after the threads stipped someone tack welded the hinge to the hood near that bolt location. Now that hinge is pretty worn and tweaked.
I've got a good set of spare hinges, otherwise the hood is pretty much mint.
should I re-tap for a larger diameter bolt? ( not sure if a larger bolt would fit through the hinge ).
Can I install a helicoil? Guy at the garage across the alley said they need a hole with a stop-point, the captured nut is open at the back.
suggestions welcomed.