I’d chop it. That nub most likey won’t grow anyways As long as you have new branches, and you do, chop away. Does look like a Mille but you need more growth to be certain on that.
I just chopped a few nubs that were only spreading, but they were healthy and I wasn't happy with some of their locations. If it's an otherwise healthy colony, whack it :) only time I don't frag is when it's already weakened (unless it's an emergency and I'm about to lose the frag anyways.