The subject in the first photo is the cutting tool on the stone. It is out of focus. The hands are mostly in focus, and the paint on the grinder is in focus. But the cutting is not.
The second photo has an ambiguous subject. None are exactly in focus, making the subject identification more difficult.
You may wish to setup your focus to a single spot, and then set your focus on the subject spot, lock it, and then frame your picture. For the first photo that may solve the problem of clear focus on the subject, which is not the grinder and probably not the hands, but rather the spinning abrasive disc on the stone.
For the second shot, you may wish to play with setting your depth of field. This might involve clearly focusing on the jewelry of interest, and having the aperture set to a large opening, like 2.8 or 1.4. Sometimes you can accomplish this with a faster shutter speed, or perhaps a ND filter. But by making your subject crystal clear, and the rest of the image compromised, it communicates your subject.
An example you didn't have, is a bird flying with a fish it just caught. The fish may be the interesting part of the photo, with the talons dug in, and the water dripping off. That may be the subject, but this is an exception to the rule, because the eyes of the bird must be in focus. That is what our visual processing and the related Human Visual System (HVS) work for. When the bird's eyes are in focus, it draws attention to the bird, and what it is doing. The talons into the fish, in this example, are the exception, in that while they are the real message, focus on them, and not on the eyes of the bird, will loose points in the exam.
PS: While you are learning all this stuff, I suggest that you use manual mode on the Nikon, as it will help you better understand the parameters. You can over or under expose the image for your subject by just throwing in or taking out a few clicks of aperture or shutter time.