My office colleague thinks I like him. How do I fix this?

I joined a new AI company recently and I've already made a pretty good group of friends. One day we were all sitting around talking about random stuff when one of my friends suddenly noticed a guy walking past.

She asked, “Does anyone know who that guy is? Is he single? Does he have a girlfriend?”

I jokingly said, “I'll find out for you.”

And somehow I became the investigator.

Whenever we saw him around the office, my friend would ask me if I'd noticed whether he was with anyone. So we'd casually look around to see if there was a girl with him.

We never actually saw him with anyone, but after a while I think he started noticing us looking at him.

Then one day I happened to look over at him and he caught me looking.

After that, my friend was still asking me about him, so I kept checking whenever he was around.

Now I think I've accidentally created a completely different story in his head.

My friend was the one who liked him.

I was just doing the investigation.

But after seeing me look at him so many times, I'm pretty sure he thinks I'm the one who likes him.

I genuinely don't know how to fix this without making it ten times more awkward.

What do I even do now? Do I just pretend nothing happened or somehow make it clear that I'm not interested?