السلام عليكم ورحمة الله أحسن الله إليكم شيخنا I prayed behind an Imam and a part of his awrah on his back was shown during sujud, it was similar to the size of of an iPhone. Do I have to repeat the prayer and also tell him? بارك الله فيكم وجزاكم الله خيرا

Ustadh AbdulAziz al-Haqqan

No, you don't have to repeat the salah. However, you can advise them.