There is no certain time or place where they start, they have been around almost as long as humans have.
Well first you stop using what ever it is you are using to clean the piercing, what ever you have been using is causing the bumps or nubs as you call them to appear. Irrigate the piercing under warm running water in the shower and leave it alone, within a few days the piercing should start to get better. By the way it's a navel piercing not a belly piercing.
only if your home is located in a body piercing business.
1920's is when American women started piercing their ears.
like when they were born
ask them how they feel about piercings before you start to ask about you getting a piercing done
-yellow/green discharge from piercing -pain or tenderness around the piercing -red, purple, or yellowish discoloration around piercing
When you first get your piercing, with any piercing, the people that do the piercing they use their own equipment and normally you choose they kind of stud you want. So yes you do have to get a stud first. Normally you have to wait 6 weeks before you can change any piercing, just so your skin can get used to it and also to decrease the risk of an infection.
To wear earrings.
Ever since they wanted to
normally it takes one-two week for piercing to get normal depending on the body's healing ..
After the first
The following day; be careful not to "over clean" it, though. That will irritate the piercing just as much as not cleaning it.