The on-loan Arsenal left-back was forced off during his side's 3-0 win over Athletic Bilbao at the weekend and will now miss the crucial Euro 2024 showdown against Spain in Seville and the friendly against World Cup runners-up France in Lille.
The news will come as a major blow to Steve Clarke, who is due to name his squad for the double-header on Wednesday, but will now need to consider who replaces the 26-year-old former Celtic star in his line-up for the October 12 and 17 fixtures.
No firm timescale has been put on Tierney’s return but with a possible recovery period of up to three months for more serious hamstring tears, he could also miss the potentially pivotal qualifiers against Georgia and Norway in November.
Socieded head coach Imanol Alguacil confirmed: "Kieran has suffered a major muscle tear. It's a shame. It's a significant injury, but it's not an extraordinary one. What I always say, each player is different and so is the recovery time.
"Time will tell when he will return, but it was a classic muscle tear that will take him time to recover from. But he will recover and we hope as soon as possible."