If this is thorium we're talking about, there is no reason to worry. Thorium is a weak alpha emitter with a very, very long half-life (comparable to the age of the universe). Alpha particles have very low penetration. They can easily be stopped by a piece of paper, or your bare skin. I seriously doubt any amount can even penetrate the camera.
This type of radiation poses virtually no threat to your health unless you eat it, or grind it up and breathe it. I assume you're not going to be doing either.
Also, given the radiation figures listed by that thread (assuming accurate measurements), if you glued that lens (literally, no camera) to your face for about 6 hours, you'd get the same amount of radiation exposure as you get every single day just by sitting on Earth (background radiation). On top of that, background radiation tends to include more strongly ionizing radiation like beta particles. So the radiation exposure you're getting right now, just sitting here, is likely a fair bit worse than any you're going to get from this lens.
It's beta emitters (moderately worse than alpha) and x-ray/gamma radiation (the real dangerous stuff) that you should worry about.