Barca were looking to give their long-serving talisman a perfect send-off before he departs for the mega-rich Asian leagues.
The hosts were forced into the first bit of defending when Adnan Januzaja advanced down the flank to pick out Willian Jose in the box, but he shot straight at Marc Andre Ter Stegen.
It was Sociedad again on the up as Willian Jose came close to rattling the net once more but shot narrowly wide on nine minutes.
Later on, a big chance fell to Barca when Gerard Pique found himself unmarked inside the box but his scuffed shot made it easy for the opposing keeper to save on 18 minutes.
On 25 minutes, Phillipe Coutinho whizzed past a few defenders before finding Ousmane Dembele, who in turn picked out Ivan Rakitic for a header, but the Croatian disappointingly failed to profit as he hammered his effort wide.
After the break and out of nothing, the opener came when Coutinho riffled home a stunning strike on 57 minutes, much to the joy of the home faithful.
Barca made the first change minutes from resumption when Dembele departed for Denis Suarez, with the lead now intact.
With few chances created in the closing stages, the Catalans staved off any inviting pressure to end their campaign on a high and give Iniesta a perfect send-off.