The Catalan giants slumped to a third league defeat of the season at Anoeta on Saturday, suffering a 3-1 reverse.
Lionel Messi cancelled out Alex Song's own goal in the first half, but goals from Antoine Griezmann and David Zurutuza in the second half secured a superb win for Sociedad.
Barca now trail Real Madrid by three points at the top of La Liga, but Iniesta is confident the reigning champions will bounce back swiftly.
"Real (Sociedad) played really well," he told the club's official website. "They were better than us; we were always trailing them.
"This defeat shouldn't make us give up. We have to work hard and turn this situation around. There are many points left, and we have games against direct rivals."
Centre-back Gerard Pique echoed those sentiments, adding: "We're just one game off being league leaders so it's not too troubling.
"These things can happen; when you attack it's possible for them to score. Sometimes you don't feel comfortable on the pitch, and you can't maintain possession.
"Their second goal was a real blow to us."
