Nikon D3100 Lens Won't Focus

[iPaperKillz]

Foreword: I am new to photography and cameras in general (seriously, like 1 week old).

I have a Red Nikon D3100 which a family member gave to me because it wouldn't focus. I take a few photos with the Auto mode and they all come out blurry. I take off the lens and look through the glass at the front (faces away from camera body) and it is clear, but I look through the glass at the back (faces the camera body where it attaches) and shine a flashlight in and there are what look to be very tiny cracks. Is there any way to fix this? Or do I have a purchase a new lens for my camera?

Picture of cracks: http/imgur.com/UxCa5AH

 

[DelroyMonjo]

Take it to a camera dealer and ask them. I doubt those 'cracks' are the cause of the problem. Does the lens barrel ever try to move on auto focus? Can you focus manually?

 

[iPaperKillz]

When I try to focus manually, I can see the difference in the viewfinder, but the photo taken is always blurry still.

And yes, when I set it to autofocus, the front part of the lens will move depending on what I point the camera at.

 

[DelroyMonjo]

Is there any way for you to try a different lens from a friend or a dealer to confirm that is IS that particular lens? If the lens is 'cracked' I suspect a defect and it should have been replaced during warranty. Was it stored in a hot environment or something?