I felt poop when I fingered his ass. Should I have told him?

I (F21) went over to my friend's (M28) apartment today. He likes when I do stuff to his butt. But I've only put a finger up there a couple of times before and not that deep (I have put my tongue in there more times than a finger). Today it was different. I started by sucking his dick and when he almost came he told me to play with his balls and then he got on all fours and I put a finger in his butt. He then flipped over again and he moved his body so that my finger went deeper and deeper. That's when I felt the poop. It was hard so my finger didn't get visibly dirty. I just kept the finger in there and jerked him off with my other hand and he came in my mouth. I pulled it out slowly as he instructed and he asked if I got anything on it and I said no. Because it wasn't visible. Should I have told him the truth?

Edit: I've had dicks in my asshole and most of the time there was poop in there. Even if I'm using the right tools while prepping. I don't know what's wrong with me. Normally I only poop like every three days. And I don't know how to make anal work for me. I told you this to make it clear to all of you that I am not disgusted by him or anything. I have caused way more mess than he did. It was okay. But since he asked if I got anything on my finger and I lied, I just wanted to know if you think I should have told him what actually happened.