Have you noticed that there is a bump on your face, but you cannot seem to pop it? Do remember that pimples are not supposed to be popped but some people do it anyway. Sebaceous cysts are hard to pop because they usually grow inwards. The pimple will grow outwards, which means that the pimple will start to show a white center after some time.
The normal cause of sebaceous cysts and pimples are dirt, oil, and bacteria. If the pore becomes infected, it may turn into a pimple. Some cysts can be found inside the body. Some of them are normal and will just go away over time. Some of them may develop and would need to be removed immediately.