My (28f) bf(31m) sent an inappropriate picture to my sister (32f) while drunk.

My (28f) bf (31m) sent a d pic to my sister while in the shower the other night. He came home from drinking with his friends and took a quick shower before getting ready to go to a different bar with me and his friends. He was already pretty drunk by then but we had a good time. Until the next morning when my sister called me and told me what happened and I was mortified. I confronted him about it and he acted surprised and said he drank so much that night he doesn’t even remember. I don’t know how I should move forward from here. We’ve been together for nearly 5 years and I live with him. I was actually feeling so secure in our relationship lately so this came as a shock. Idk if it’s worth salvaging or not. Any advice of what I should do? Is it worth trying to save? I’m not sure how to build trust back up not to mention how awkward it will be with my family now. TLDR: my bf of almost 5 years sent a D pic to my sister when drunk and idk how to react.