Need advice on a Polish guy friend i got with

Hey, so I'm 16 and I've known this guy who is 19 for 2 years, he was going out with one of my best friends for like a year and a half until about 3 months ago when they broke up, the other night me and him agreed to meet up and chill, however surprisingly we happened to kiss and well do stuff, do I tell her? Am I supposed to feel guilty? Am I the one in the wrong? Please someone help me..

When I'm with him he makes me feel safe, and he's such a good guy, I don't want to let my chance slip by..

If you end up with him you might lose your friend, unless she's very understanding. So depends which do you care more about, the guy or your friendship.