What would you do??? PLLLEASE?

ok here it is . Im dating a man for the last two yrs. I love to have fun go out party, work and just be me. I Never cheated on him and Never plan it. I have this guy friend since grammar school. Never touched him, and never will. I mean he's totally not my type, no attraction , nothing. I mean its like day and night. We occasionally go out dinner, bars etc. we go out. He talks to girl and me , i just have fun ya know i do my thing. Let me just tell you this guy is is BIG Time. You know what I mean.( dirty money) I mean it doesn't matter to me I have my own. Ok so last night he calls me . Im doing laundry and he's like Im leaving for 2 weeks and I wanna give ya something. So i left my man at home To go meet this dude. i was gone for like 15Min's. He hands me a bag, and says I gotta go talk you later. Ok so I get in my car and look in the bag which has a bag in thee from K-Jewelrs. Then a lil box in there. I couldn't think for a moment and told myself WTF????? out loud. Well iM female so I open it. And there's a diamond ring inside. And people its not your average diamond ring. I mean its drop dead gorgeaous. and had to at least cost 2-3k. and no its not stolen if thats what some might think since he's big time (ya know the underworld) it had all the recpt and what nots. OK SO SHOULD I KEEP IT OR IVE IT BACK COME ON SOME ADVICE HERE. I asked why and he said that I was a grea and understanding friend.