Does anyone know how toxic the cured resin can be? Is it safe to make jewelry that has constant contact with the skin, such as rings? I’m interested in creating some fashionable wearables as well that will have constant contact with the skin.
Just don’t eat it and you’ll be fine 
Not very.
(As long as it’s well cured, it’s fine. If it’s not cured well, it will be an irritant.)