I hate lancing things in humans, even though I am trained to do it. Usually, I have found some poor sucker, usually a family practice doc, who is willing to do it in exchange for my seeing a screaming baby.
First, it hurts when you lance something, so people often move and scream. Second, if it is an abscess but isn’t quite ripe or you don’t hit the right place, no pus comes out. Then, you have to stab the person again and hope you find the right spot on the second try. Even if you get the right place, you have to break up any loculations/areas of tissue that keep the entire abscess from draining by moving a sterile forceps around inside the abscess. Then, you have to decide if you put in a drain so it will keep draining any residual pus. In people it is good to culture the pus. That way, if the person runs a fever, or the cyst stays infected, you know the best antibiotic for the infection. A sterile surgical blade and good, clean, technique, are important parts of the procedure. Sometimes, the area is so painful that strong pain meds or sedation are needed before draining the abscess.
Sticking a knife into a possible cyst is not something I would do to my own dogs.