BAD IDEA
Can I pick boogers in public?
Yes, you can, but only if you want to become a social pariah.
Technically, you can pick boogers in public, but congratulations on broadcasting your nasal excavation to everyone nearby. It's widely seen as gross and socially unacceptable. If making people cringe and lowering your social rating sounds fun, go ahead. Otherwise, save it for the privacy of your own space.