What is a nickel with a head on both sides is this considered a mule coin Is it worth anything?

What you probably have is a novelty coin made by machining two coins to fit together so to appear to be just one. They have some value but it is generally limited to whatever you are willing to pay for them. However, new things are always turning up in the coin collecting world so I would suggest to take the coin to a coin shop and have them verify what it is.