Grain at 100% should not be much of an issue. If you are viewing at 100%, you are looking at roughly a 1000 pixels out of more than 6000 in width. That means you're looking at the equivalent of a 6 foot wide print from about 18-24 inches away.
You can always apply a little noise reduction if it bothers you. The most likely sources of noise are initial sharpening or download settings. If you sharpen or apply contrast, it can increase the noise.