I got involved with a coworker, and now I'm blocked. I'm not sure how to proceed, any advice?

I apologize. This might be quite long. A bit of background: I (24f) have a coworker (25m), we'll call him Bobby, that I've become friends with over the past few months. We would occasionally use whatsapp to send memes to each other.

Now for the problem: About 2 1/2 weeks ago, Bobby started messaging me more, which I thought was odd because he has a girlfriend. His messages took a turn to the flirty side, and I brought up his gf. He said she's not a Saint either, and he's just looking for some fun. In the past, and currently, I've had issues with self-esteem. So, any attention I receive is hard for me to walk away from. Especially when it's somebody I'm already familiar with and I've been attracted to. I stupidly went along with this, we switched to snapchat, and things got pretty heated for a while. There was nothing in person, nothing physical, but there was a lot of explicit messaging involved with plans to meet up. I know this was wrong.

About a week ago, he left me on delivered, and three days after that, I noticed he'd un-added me on snapchat. I was on vacation until yesterday, and our first day working together since was today. We work very closely with each other and the rest of our team, we ignored each other the entire shift. I'm not sure how to proceed at work while interacting with him. We were quite talkative and close before this. If we continue ignoring each other, I'm worried someone will notice. However, I have no idea how to simulate normalcy.

How should I continue?