Tailgate bolt stripped/rusted, what should I do?

Went to tighten the bolt on one side of the tailgate and it wouldn't budge, and then boom, it just started to spin freely and the threads won't grab. Thinking it might be stripped from the inside? Do I have to get new threads tapped into the bed?

Video and pics for reference:

https://imgur.com/a/APtQldn

 

I think the nut on the backside of that is tack welded to the body. Pop the light off and see what you're up against.

 

Im Having this same problem, that nut is tack welded. If you take the tail light out you can look down and see the back side of it. Its a bitch to grind that nut off if you have to so be very careful.

 

I took the tail light off and my nut wasn't even connected to the body, so the weld must not have been very good. Just replaced it with a new nut and bolt

 

It's a tack weld to keep the nut from spinning, not a full structural weld.