Man asked my son if he could suck his toes- Should I call CPS?

I need some advice on whether to call CPS.
I have a 7 yr old boy who I and his mother share custody of. We are not together. I am married and she has a boyfriend. The issue at hand stems from something his mother, and her boyfriends friend asked my son to do.
My 7 yr old son opened up 3 days ago and out of no where said to my wife and his brother and sister "you guys want to know the creepiest thing that happened to me this weekend?". Then continued saying "It was so CREEPY! This man asked to "SUCK MY TOES"!". He briefly paused and said "Two Times" before my wife immediately interjected and said "What?! That is NOT ok at all!"
I was not there when this happened. My wife told me about it when I got home and I then had a talk with him about it as that's very concerning. At first he didn't know what I was talking about.... although he did. I think he was just embarrassed to tell his dad. After he spoke to my wife for reassurance he then told me everything. He said the man asked him on 2 separate instances that day (once at the pool and once at dinner) if he would suck on his toes. I asked if his mom was present during all of this and he said yes. I asked him why this made him feel so uncomfortable and he said that it was embarrassing.... *which is why I assume he didn't tell me initially when I asked him about it.
I have since brought this up to his mother asking for this guy's information and she has declined to provide it. She's ignored every message I have sent to her since we exchanged our son 2 days ago. I'm getting no help or information regarding this at all. My lawyer suggested I call CPS to intervene but that she couldn't tell me what to do.
First off... this is very concerning to me. I don't know who this individual is and no grown man should ever say that to a young boy.
His mother and I don't get along and are at the conclusion of a child custody case that is set for trial in December.
Should I call CPS?