The sound was interesting too, actually. Odo wondered what kind of vocal chords he would need to form to mimic that sort of vibration. It's hard to keep his eyes off Toothless, and curiosity gets the better of him. He hesitates, then asks;

"May I approach him? I'd like to take a closer look, if possible... or should I be asking him instead?"

Odo looks from Hiccup to Toothless and back again. He wasn't sure about the level of the dragon's consciousness, and he didn't want to be rude.