I agree this looks like a bit of camera shake. Your EXIF data says you were zoomed to 34mm -- normally 1/100th is more than fast enough for that focal length even without any form of image stabilization -- but those guidelines are based on an assumption that you're at least trying to be somewhat steady and that you've got good technique for that.
It's also possible that it just missed focus. Off the top of my head, three things can cause this.
1) If the camera gets to select it's focus point and there's a distracting element which is CLOSER to you then your intended subject, the AF system will always try to pick the NEAREST object where it can lock focus. This isn't the issue with this particular shot though because we'd see that "nearer" object. If there is a possibility of distracting elements ruining the shot by causing the camera to focus on the wrong thing, then pick your own focus point rather than letting the camera pick it.
2) If you are in "One Shot" mode then two things happen: (a) the camera will not take the shot until it can confirm that it has locked focus (that's called "focus priority") and (b) once the camera does lock focus, it shuts down the focus system. That means if either you move or your subject moves after the focus locked, it will NOT re-focus the camera... the focus distance will be left at whatever it was originally locked at. You can release and re-press the shutter to get it to re-evaluate. You can also configure an alternate back-button to demand that it re-focus whenever you press that button (very popular among sports photographers.) It's unlikely this was the problem in this case unless you locked focus and moved substantially.
3) If you are in "AI Servo" mode then the camera switches to "release priority" mode (which is the opposite of "focus priority" mode.) In this mode the camera WILL take the shot as soon as you FULLY press the shutter button and it will do so whether it was finished focusing the lens or not. Basically "release priority" means when YOU press the camera shutter release button, it WILL release and snap that shot even if the camera wasn't really ready. This mode is popular for sports photographers because YOU (the photographer) know what you intend to shoot and the camera doesn't. If a distracting element gets in the way and you know the camera is focused for your purposes then you don't want it second guessing you, blowing the "decisive moment" when you needed it to fire and refocusing to some wrong/distracting element in the frame. You'd be using impolite and colorful language with your camera if it did that.
I suspect it was actually camera shake.