a new leaf sprouted out of the bud.
However, it looks pretty much like a new plant is growing out of it.

I would let it alone. It is probably just growing a new branch. You may be able
to root it a a cutting in the spring, but wait until it gets much bigger and
spoils the outline of the tree.
Iris,
Central NY, Zone 5a, Sunset Zone 40
"A tree never hits an automobile except in self defense." - Woody Allen