In a horrible teenage bestfriends & guys situtation! PLEASE ADVICEE!!!!!!?

longgg story, but ill make it short. This guy, Nico, that i recently started like again after not seeing him in like 2 yrs, and he just started to like me, we kissed today. So i got to tell one of my close friends because i was really exsited and she tells me she thinks our other close friend, Elizabeth, likes him to, because they used to have a 'thing' and she really liked him. Though i didnt know anything about their 'thing' , & i just found out. i called Elizabeth to make sure shes not made & ask if she still had feelings for him. she was in shock and still does have feelings for him. She also told me that she did tell me about thier 'thing' but i dont recall it not one bit & if i did know , i would never have done that. I relize now i screwed up, & now i dont know what to do. I fall into 2 wrongs. I could eathier continue my thing with him because i do like him, and he likes me.but then i can only hope me and Elizabeth will still be friends ( but i dont wanna do this because i love her and i dont wanna loose her as a friend) or i could make her happy and tell him i cant talk to him anymore because my friend still had feelings him , but then that makes me & unhappy. i know i shouldnt be selfish, but wat should i do!?!??!!? pleasee noe rude comments!? what should i tell them? thanxx in advanced.