anal sex

so last night i had anal sex with my SO. he asked if i wanted him to cum in my ass and i was just really into the moment and i said yes. i wiped myself clean after but i couldnt tell if it was just wet from me, or if it was his cum... i havent had anything on my underwear or anything either.... should i take plan b? or (this might sound stupid) is it like stuck up my butt?