Thanks @LaBlondehow long has it been since your date? you say that you haven’t spoken much since, but how long are we talking? also don’t feel like he should have “expected more to happen”, you don’t owe anything.
i’m not sure how i would feel about dating a friend’s best friend tbh! i feel like i would worry if something happened, if something went wrong - and you mention that your friend already messaged both of you to see how it had gone and already knew what had happened because he’d told them. i’m a fairly private person so i feel like that would cause me some anxiety.
it’s ultimately up to you! your wording is that you’re already anticipating that it may be awkward and our gut feelings are usually correct - but if you really like him it may be worth just (if it goes further) setting some boundaries with your friend as to how much you’re comfortable sharing. if that makes sense!