They were pricked in their heart (
katenughsan thn kardian). Second aorist indicative of
katanussw, a rare verb (LXX) to pierce, to sting sharply, to stun, to smite. Homer used it of horses dinting the earth with their hoofs. The substantive
katanuxi occurs in
Romans 11:8 . Here only in the N.T. It is followed here by the accusative of the part affected, the heart.
What shall we do? (
Ti poihswmen). Deliberative subjunctive first aorist active. The sermon went home, they felt the sting of Peter's words, compunction (
compungo). Codex Bezae adds: "Show us."