Pimple Turned Into Hard Bump. When a pimple or zit is popped there is usually liquid pus within the pimple but sometimes there is a hard substance. An acne cyst also goes below the skin and is filled with pus as well as skin oil and dead cells.

Hard acne bumps come in two types. These germs are usually harmless and normally found on the skin of healthy people but can cause infection if they find their way into open cuts or scratches. A melanoma pimple will typically present itself as a firm red brown or skin-colored bump that many doctors may misdiagnose as a pimple or harmless blemish.
Changes in hormone levels.
A warm compress can help your pimple open so it can release pus and start to heal. No matter what causes the break it triggers inflammation in and around the follicle. Its especially effective for pimples under your skin. Increased levels of testosterone in men and women can trigger an increased production of sebum.