Hep my dog just ate chocolate!?!?

I was gone for a few minutes and when I came back my dog had jumped up onto the table and she ate one of those mini Hershey bar things, the tin wrapper included, I did wrench some of it out of her mouth but I don't know how much she ate, I think it was just that one and she looks fine right now and isn't acting weird but I don't know what to do!! Help!! :(