Tattoos are quite painful for some people, while for others not so much. Also, they may hurt more in certain parts of the body.
Factors that can affect pain levels in a tattoo include:
the location of the tattoo
the size, shape and composition of the design
each person's pain tolerance levels
the gender
The human body "rewards" us with endorphins to deal with pain. So the procedure usually hurts for the first 5 – 10 minutes and then you either feel a numbness or you suddenly feel really good.