Ganglions are common. Many are painless, and all are harmless.
The back of the wrist is one of the commonest sites with the palm side of the wrist a close second.
They are a balloon of thick jelly like material. The source of the goo inside is usually a ligament in the depths of the wrist.
Bursting a ganglion by hitting it with a blunt object, for example a book, may burst the balloon but the material inside continues to be made by the ligament, and the ganglion fills again.
It is difficult to drain the thick jelly through a needle, and again the ganglion likely will fill again.
If a ganglion is annoying enough, for example by hurting when doing pushups,writing, yoga or surfing, then surgical excision is the best option. This involves removing the balloon part of the ganglion, and switching off the source in the ligament by debriding or gently cutting out the small portion of ligament.
The main risk of surgery is a small chance ( 5-10%) that the ganglion can return.