No it's not bad to pick your nose as long as you do not eat your boogers and you wash your hands often after you pick your nose.
If you pick your nose and then prepare food or eat the food then you can introduce germs into your own system and into other peoples systems.
So as long as you avoid touching food after picking your nose and provided that you wash your hands after you pick your nose then it's not bad to pick your nose.
I pick my nose sometimes myself when I have hard boogers in it and then I wash my hands within a few minutes of doing so.
Sometimes you have to pick your nose to get the harder boogers out.
I used to pick my nose and eat it as a toddler because my mom has pictures of me doing that.
I would also sometimes pick my nose and wipe it on furniture.
Not now though as that is gross.