My husband and I went to his female friends house gathering last night and it was awkward for me as I didn't no anyone but her. He left me in the front room with people I didn't no for around

20mins. When I went to look for him he was in the kitchen with the birthday girls sister and 2 others who was talking amongst themselves. The sister was cutting cake with her back to him but he was leant against the side arms crossed watching her ass! When he saw me he had that shocked look on his face. I didn't say anything at the time but now im in bed and can't sleep. Should I say something when he wakes up?