i just popped a pimple that has been developing for a while

[Iz68689]

im 15, have not had my period yet, not sexually active, and take showers regularly, and i use razor blades for shaving, this it my first time seeing this happen, and ts maybe an inch or two below my waist line, thank you

[Gemfly]

If you shaved there it could be from an ingrown hair.

[Harv_c]

Now that you have lanced the pimple it should heal up.  Do not continue to pinch it, you will push bacteria inward.  Wash it several times a day until it is completely gone.  If you have any acne type wash use it.  
Since you did not ask a question I will assume you are concerned that more will appear.  
A bump commonly called a rising can occur anywhere on your body where your skin pores are closed and your natural oil cannot escape.  Upon noticing one, start washing it several times a day with hot water and soap, again an acne soap is best.  You mentioned waist line so I will mention tight belts or gripping cloths can help close these pores.
You mentioned shaving and anywhere you shave with a razor can get ingrown hairs.  This is where the hair starts to grow back but cannot push through the skin.  It can make a small bump that can hurt as well.  The key here is to use a body cream which mentions use after shaving or any cream is better then none.  
You also mentioned showers, so be sure to always scrub every inch with a wash cloth or similar.  Soapy hands will not remove dead skin or dried oil that clogs pores.
Feel free to send me a message if you need more detail.