Hosts Hannover made a promising start to the match, but Hertha had a goal ruled out for offside when John Anthony Brooks converted after Ron-Robert Zieler parried Sebastian Langkamp's shot.
Zieler was back in action to push Genki Haraguchi's volley behind, while Salif Sane and Jimmy Briand missed chances for Hannover as the half ended goalless.
The opening goal came in scrappy fashion with 15 minutes to play as Hertha failed to clear a corner and Christian Schulz bundled home amid suspicions of handball.
Hannover's advantage did not last, however, as Stocker - who opened his account for Hertha in last weekend's 2-0 win over Paderborn - crashed home an acrobatic strike from the edge of the area to earn a share of the spoils.
Hertha are 11th in the Bundesliga - three places and two points better off than Hannover, who are 14th.
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