Did you by chance spill something onto the trackpad? If you did you may want to try cleaning the area. Carefully moisten a paper towel with some kitchen counter cleaner like: '''[http://www.soap.com/p/fantastik-multi-purpose-cleaner-51082?noappbanner=true&utm_source=Soap_SG&utm_medium=PDP_SG&utm_campaign=so-sg-to-mobile|Fantastic]''' Remember! '''Don't spray any cleaner onto your system, wet the towel''' you don't want the cleaner to go to far here.
Once your sure the trackpad edge is not gummed up so it can move you may need to adjust the click plate from the inside. Sadly, you'll need to remove the glued in battery to get to it which means you'll need to replace it in the process <Ouch!>
Frankly, if cleaning the top didn't free it up I would get your system to an Apple Store for them to repair it. It might even be covered under warranty!