trackpad mouse button sticky

Hello

 

My left mouse button is a little sticky.  I was eating an orange and it squirted on the mouse button. I didnt clean it up because I didnt think it would have any effect.  Now, the button makes a little noise the first time I use it each day.  It's fine after clicking a few times. 

 

Could someone please recommend how to clean it?  Are there directions as to how to open the case?  Thanks.