Keep in mind surgery may also be in order cysts that rupture have a tendency to rupture heal fill back up and rupture again removing the sac that fill is the only cure and in the case of repeated cycle it is far more dangeriou to the dog to have to deal with the possilbe infection etc than the risk of the surgery.
I dealt with this repeatedly with both Sadie & Spencer. Luckily, only once was surgery required. Spencer had one on his back that just would not heal, so it was removed. All the rest drained & healed on their own (with a round of antibiotics).