LOL, there's a joke in here about me eating an entire egg's-worth of Silly Putty when I was 6 years old, I used to eat PlayDough too (thank God all of these things are all completely non-toxic, or I'd have died long ago)...Seriously, I have to hear these stories still today. So it's definitely non-toxic, as I've eaten plenty of it...why am I telling the public this...
Anyway, as AHBD has already said, whether or not this is a problem is going to depend on how much of the Silly Putty your dragon ate, and how old he is and how large he is. If he only ate a little tiny piece of Silly Putty it should just come right out, but if he ate a big chunk of it, or god forbid he ate the entire egg's-worth, or if he's a baby or small juvenile, then this could result in a bowel impaction, as I don't believe that Silly Putty gets broken-down, it just comes out whole...