Yes boogers that come out of your nose are dirty and do contain lots of bad bacteria that needs to leave your body.
Although eating boogers is supposed to boost your immune system you should not eat your boogers as it's gross and not a good thing to do.
The boogers are unlikely to make you sick if it's your own boogers but still it's gross.
The boogers contain bacteria and germs that your body wants to get rid of and introducing those germs and bacteria back into your body is a bad thing.
So when you pick your boogers throw the boogers away or flush them down the toilet and wash your hands before touching anything else.
I used to eat boogers as a toddler and kid and stopped eating my boogers when I turned 9 years old as I found it gross after that.