The smell is from the secretions of the cyst -
https://www.everydayhealth.com/sebaceous-cyst/guide/
"And as for that secretion that can emerge from the cyst? It comes from the cells that form the walls of the cysts. Those cells secrete a protein, known as keratin. These cysts are also made of fat, and it’s often that substance, or infection, that makes the smell, according to American Family Physician."
Do not try to pop it like you would a pimple. You can try a warm compress on it and see if it will drain on it's own, but doing anything else can cause it to become infected.
Where on your body is this cyst?
Does it look infected? Is it red? Hot or warm to the touch? Do you have a fever? Feel bad? Feel sick?
If any of those are yes, get medical care. Even in a poor medical system, they can treat an infection.