They told me they stutter - What do I say?

They told me they stutter - What do I say? I met a new friend at school and they told me that they stutter. I didn't really know what to say because I didn't want to offend them, so I just nodded. Maybe I'm just being silly but I felt bad for not really acknowledging it. I didn't want to ask them how long they've had it or if they hate it or accept it, I didn't know at all. What should I have done?