hi its totally normal to get little bumps under there, its part of every girls development, and dont worry its not cancer.
I'm sorry i didn't mention this before but i'm actually a female.
Hi,
Yes, that is common for many boys of your age.It is due to the testosterone being converted into estrogen to give you growth spurt and would vanish in course of your pubertal development. Read from the following link more about pubertal development and especially read under ' Hormonal changes in boys ' where specific mention of this effect is mentioned:
http://en.wikipedia.org/wiki/Puberty
Neverthless, do mention this to your doctor during your next physical, so that he could reassure you.
Solace