So I discovered I missed some mold lines on some of the minis after I primed. Should I go back and scrape them off and hit the miniature again with my primer? Or is it too late?

Its never too late, if they annoy you then just scrape them away the prime again over the areas you scraped!

Depending on how cleanly you can remove the lines you might not even need to prime again. Paint sticks to itself horizontally as much as it adheres to primer paint in layers. As long as you don't have any large gaps the paint will bridge over and stick to the even if there's some small gaps in the primer coat.

You don't need to prime over again.

Ya a few layers of whatever will cover it up