D3100 camera repair?

So I recently took my camera to a trip abroad and I noticed that the images were somewhat fuzzy. It seemed to have trouble focusing on subjects on different settings. Is there a recommended place to bring my camera and see what's wrong with it? Or should I just send it back to Nikon through their support website and then they send the camera back? It's not under warranty, so I don't know whether it's better to bring it elsewhere. Any adbice or suggestions are appreciated. Thanks.

Have you checked your sensor? Have you performed a sensor clean procedure?

There are probably camera places around that could fix it. Not sure where you are from, but there is 1 authorized service center in MI that I know of. Otherwise, can't go wrong sending it to Nikon if you KNOW it needs repairs. It takes a bit longer, but you know it's being done by Nikon.

Is the lens in auto mode? Do you have a different lens to try? It could be a lens problem. And are you sure its not a camera setting? Try single point focus with the point in the center and have it on the subject. That might be obvious, but I've seen some beginners accidentally jog the focus point to the side and then have focus problems.

What was the aperture and shutter speed....It may well be slow shutter speed and camera movement or your technique..

Post a few pics with the exif data then we have better info to work with...

I'm not sure how to do a sensor clean procedure or how to tell if the focus is set to the side....I'm a beginner. I think I will take it to a camera repair place somewhere first and see if someone can take a look at it and tell me what's wrong. Thanks for all the replies.

If you have a friendly shop that won't charge you, it might be good to have them look at it quickly and see if it is a settings problem. I would not pay for a service until you understand how your camera works so you can be sure for yourself it is just not a wrong setting. While your camera has some automatic modes, it is not a point and shoot and it has settings available to you that could be set wrong for a given situation.
As far a focus point being off to one side, I was referring to the possibility of you being in single point mode and unknowingly moving that point around the screen with the arrow button. You have 11 points and can choose any one in single point mode. Accidentally choosing a point off center can cause unexpected results. In fact, just not being familiar with your focus modes will cause unexpected results. If none of that makes sense, then you really should get familiar with those settings. They are basic 'everyday tools' that are available in your camera. @pedroj mentioned camera shake and settings, that is a good possibility too. How are pictures in Auto mode? Auto mode will eliminate some possible bad settings, but focus mode might still be an issue. You could try resetting the shooting and setup options as described in your manual. Post some pictures if you want and we can take a look. If you post pictures, list ALL of your camera settings.

A couple years ago, I once took some shots with the lens set to Manual instead of to Automatic as the camera was. It took a walk back to the car, to figure out where I goofed up.