Some juice from an orange went down the wrong way.what will happen to the juice?

It gets absorbed: I take it from your question that some orange juice went down your trachea, or airway. We call this aspiration, and unless it was a large amount or happens repeatedly it is not likely to cause any problem. It is acidic, so will be even more uncomfortable than other liquids in the airway, but will be absorbed into the body. There is a small chance it could cause a pneumonia, but this is not likely.