The worst soreness (the stinging) goes away after a day, getting better every hour. The pain peaked for me about 15-30 minutes after getting it done.
And expect to sleep on your back, shirtless, for two - three nights, because you will remain sensitive. Any tugging or bumping will hurt you for a few weeks, and after that you will be pretty resilient and healing nicely.
Yes. Any piercing is going to hurt to some degree.
It varies from person to person, depending on the size of your nipple.
That you decided to get a nipple piercing.
Well that depends on gender, male or female. Male nipple piercing is momentarily intense due to the lack of actual tissue. Female nipple piercing is also intense but my client say that it's a diffrent type of intense (not so much pain)
How long has it been pierced
I can see no benefit from doing this. It would hurt like heck and is harming yourself for no real purpose.
It is best to wait about 6-8 weeks like you would with any other piercing :)
You can get it done again once you're sure the piercing is healed inside as well as out.
As long as you are taking care of it nothing would happen and it should be fine.
The jewellery needs to be 2 mm longer than the width of the piercing.
Many are motivated to get a nipple piercing for personal reasons including for self-expression and to feel unique.
Yes, however it should be noted that tongue piercings are one of the least painful piercings to get.