My crush smiled at me and I messed up

I was talking to some of my colleagues the other day and my work crush approached us. I looked at him and he looked back and smiled really sweetly but I was caught a bit off-guard at his smile and was not expecting it so I looked in another direction quickly before I could process what had happened and then he started talking to my other colleagues.

I feel like I've really messed up now as he might think I'm uninterested whereas I'm just shy. I also won't see him for at least a week now and I don't see him much. Have I ruined my chances with him and what can I do do show him I am actually interested in him without telling him outright?