I say go for it - worst case is he doesn't remember you - and it's doubtful - it sounds like you made a (good) impression. Second worst case is he says "oh gee sorry, I don't have any openings right now".

I'm terrible this way too - I'll offer something like driving someone to the airport - and *absolutely* mean it - but when someone else offers me the same thing, I'm so much less likely to take them up on it, because I feel like I'm imposing so much.

He wouldn't have made the offer if he didn't mean it - at least at that moment No harm in shaking that tree!