The creature you sacrifice for the ability of Stitcher’s Apprentice could be the Homunculus you’ve just created. It could also be Stitcher’s Apprentice itself.

You create a token and sacrifice a creature all while the activated ability is resolving. Nothing can happen between the two, and no player may choose to take actions.

Any abilities that trigger on the Homunculus token entering the battlefield will resolve after you’ve sacrificed a creature.