Your BP should be fine. And it shouldnt be poisionous/toxic, the pet store wouldnt sell it, I dont think. I use repti-bark, and my bp has swallowed the bark several times from striking wrong. Since snakes have very strong stomach acid, the snake should be fine, he may have trouble digesting it depending on the size, but since you said it was small he should be fine. Actually, my bp has swalled multiple wood chips, and digested them fine. Dont worry, also, I would NOT recomend repti-carpet, I heard its a pain to keep clean and when they poop/pee it smells terribly.

If you want to switch substrates I would recommend aspen, which is softer than reptibark and more safer, or if you are worried you can always switch to newspaper/paper towels although it doesnt look so pleasant. hope I helped