First, I suggest that you do not try using any type of liquid to start out with in the lens area. Get a can of compressed air with a fine tip and blow out the space between the cover and the lens barrel. Any residue hampering movement (possibly even a single grain of sand) could be keeping it from opening and closing correctly.
You can also take a look at the link below for some generic suggestions to dealing with this problem.
Next, I would contact Nikon support directly by phone, (it is still covered under the one year warranty). They should repair or replace this camera for free.
Please keep in mind that my diagnosis & solutions provided are directly dependent on the accuracy of your description of the problem. As with any "do it yourself" fixes, success is a "team effort", since I can't see or touch the camera, and relies on the customer's manual dexterity and ability to follow the instructions well.
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