my stepdad walked in on me

so this just happened twenty minutes ago and i need other peoples opinion on this to make sure i shouldn't overthink it. i've only known my step dad for a few months and he just recently got married with my mom and moved in. and so i needed to go to the toilet and he was coming up the stairs and i think it was clear that i was going to the toilet. so i sat down and started to pee and i'm pretty sure i locked the door but after a minute or so of sitting in the toilet he opened the door and was staring down at me but we both quickly apologized and he quickly shut the door. idk i just feel weird because i thought he saw me go in and he didn't even knock even tho my mom is always like how i should knock everytime i go in so shouldn't it apply to him? should i tell my mom or should i just leave it?