Should I tell my boyfriend what happened?

I’ve been in this relationship for three years, ... im 26 yrs old, my boyfriend is 34. I met another guy, at work, we became very close.. finally he told me he is in love with me and he kissed me! .. of course I let it happen.. I returned the kiss.. the thing is I dont know what to do now. My current relationship it’s been trough many things, we’ve had issues, we’ve solved them, and we just have lots of fun together.. but there’s something this other guy told me that I just cant forget.. because it’s kinda true.. he told me he is the one I run to whenever I have whatever problem going on, like he’s the one I talk to everyday and all that.. he told me I am already cheating in a “emotional way”, and that he’s more my boyfriend than .. my real boyfriend. I know it’s like.. “hey you should just tell the truth to your boyfriend, be honest..” but I’m just not so sure it’s the best thing to do.. this is the first time something like this ever happened to me, and I’m just so confused.. should I just keep my mouth shut and figure it out like on my own first??? or should I just come clean and, tell my boyfriend what happened? knowing that he is going to be very pissed, and that if he still wants to be with me, he’s going to be stressed forever about me and my future co workers, specially since he’s moving to another city??