Idk what to do😳

Okay so me and my friend have known each other for years. Well, she's has been dating this guy for two years and has a child with him. Well he told me that a few days ago they broke up because she would not stop talking to her ex in jail, even telling this guy she was in love with him and all these other things. So her baby daddy told me he couldn't handle it and ended their relationship. (They still live together though and sleep in separate rooms and she's had a "guy friend" come over almost everyday for a week) Anyways I've always been there for her and her baby daddy, me and him were friends, he seen me as somebody he could vent too. Well, night before last he started Snapchatting me and we were just talking back and forth, well he randomly sent me a Snap about him being single, I was like oh wow I didn't know you and ******* broke up! Then he told me what happened and we were just talking about her and how she would rather have a guy that's in jail instead of the guy that has done everything he can to take care of her. Anyways I'm not going to lie he did start flirting with me and I did some flirty emojis back (not anything really bad) so next thing I know he says something about how he just needs to go out and have lots and lots of sex, I started feeling uncomfortable and just kind of brushed it off and was like well you go do that then. Then he started saying things that made that comment towards me. Well after a very uncomfortable situation he told me he wanted to send me something but wouldn't tell me what, then he said u ready? And I just said suuuure (I wasn't really) he sent me a dick pic. All I could reply to that was 😳 and he made me promise that I take it my grave and it stays between me and him. I was so weirded out I even told him that, he asked for a picture in return and I told him I'd prefer not to send him one and he said, well I'll see you around 👍🏻 and I just said okay 👍🏻. And I literally spent the rest of the night without sleep because I was just so bothered and weirded out by it. (I didn't think he was the type of guy that did those things so it had me in shock) Weeeell my friend doesn't know about any of this and it's a few days later and I honestly feel REALLY guilty over and I didn't even do anything wrong. I don't want to tell her but she's been trying to call me and I can't even hear her voice without thinking about it, we were supposed to hang out this week but, I can't look him in his face or hers. It would just be so awkward.🤦🏻‍♀️ Idk what to do I really don't want to tell her because no matter what I tell her she will turn it into my fault (she's always done stuff like that) not to mention for some reason she's thought me and him have liked each other for a few months, so that will make it worse. (I don't like him at all like that.) I just don't know what to do.😭 I feel like a god awful friend.