What has the age gap got to do with anything? 7 years is nothing, I could understand if he was 27 years older than you!
Would you even be considering leaving your b/f if you hadn't met this guy at work? What if you do leave him and it doesn't work out with the other guy, would you be wanting him back?
Do you love your boyfriend? If you do, is it worth ending your relationship over a crush on some bloke from work? If you don't love your b/friend then maybe you shouldn't be with him anyway, whether you have met someone else or not.
As Redhead24 says, do the decent thing either way and do what you think is right but don't cheat on him.