Excessive headspace creates a dangerous condition. A bit tight, on the other hand, isn't an issue so long as the bolt will fully close.
Personally, I'd probably just go shoot the thing, see how it does (making sure, of course, that the bolt was fully closed each time for awhile). The high spots on the lug engagement surfaces will wear in. I've put together a couple that were real snug, to the point that you could let the bolt go and chamber a round, but extracting it required a tap on the CH with a mini deadblow or small piece of wood. Guess what? After a mag or two, they smoothed right out, was able to easily hand cycle rounds.