my boyfriend ran into an ex-hookup of mine

i'm 22 and just graduated college while my boyfriend is also 22 but goes to a diff college that he'll graduate from soon. about a year ago i had hooked up with a different guy from his college. we had sex once and that was it, i haven't see him since january 2020 and we haven't talked in quite a while, despite the fact that i know he still liked me. i made it very clear to my ex-hookup that i was in a new relationship with my current boyfriend. however, the two of them bumped into each other today (they vaguely know each other through friends) and talked, and all i know is that my ex-hookup talked about me. my boyfriend seems to be shelled up and not wanting to talk about it, he told me he doesn't want to be mad but that he feels absolutely horrible right now and that there was almost a scene. i have no idea what my ex-hookup could've said about me aside from the fact that him and i had sex once, which my boyfriend already knows about (i had disclosed it to him early on to be as honest as possible when we realized we both knew him). i really don't know what to do and i'm extremely anxious that my boyfriend won't tell me what happened. i feel like i didn't do anything wrong, i hooked up with this guy months before meeting my boyfriend but i'm scared that my ex-hookup lied or exaggerated something and i'll get made out to be some horrible person. what should i do?