Everyone does it, but we don't have to offend.
There are certain things we all do that we find inappropriate to discuss, and nose-picking is one. Whether you're scratching your brain, doing a little mining, or pointing at your imagination, picking your nose is not something that the general public should see.
The Nasal Academy
Now, why in the world would any self-respecting human being scratch around in his or her nose? Because it is really a part of healthy daily hygiene; that's why. The issue comes when this activity is undertaken in front of others or in a way that could potentially cause the spread of disease.
There is nothing more natural than to scratch an itch as soon as it is noticed. However, in the interest of preserving dignity, I have a few suggestions that can minimize your impact on society while still providing relief.
Move to a private location. If you are in a meeting, at dinner, or just hanging with friends, politely excuse yourself and move out of visual range before taking care of your issue. Even if the rest of the room just doesn't understand, pursuing privacy in this situation far outweighs any frustration felt by the other parties.
And when the itch begins, the tendency is to use one's finger to relieve any discomfort. However, there is a double edged sword of hygiene that must be dealt with. You must be concerned with your own susceptibility to germs as well as the possibility of you passing germs on to someone else.
An easy way to kill both of those birds with one stone is to use a tissue. A tissue can provide a solid barrier between your finger and any germs, and can then easily transfer those germs to a trash bin. That's not all, though. Be sure to wash your hands with soap and warm water after the deed is done.
Now, I don't usually carry around a restroom sink in my back pocket, but I can tote a small container of sanitary wipes that are just as effective. Protecting your health and the health of everyone else with whom you might come in contact is only mannerly.
What if You See Someone Picking Their Nose?
At times you and I might come across someone who is picking his nose in a meeting, at the table, or behind a food counter while making a sandwich. Don’t panic. If you are in a setting where offering a tissue or napkin might be appropriate, please do so but with grace. Pointing out someone’s flaws in public will not win you any etiquette points.