Nasty looking thing you have there Soflsun. And to think it was twice that size before you bashed it! Ouch!
I'm sure you'll have looked this up already but here's what Wiki has to say about treatment:
<div></div><div id="QUOTEHEAD">QUOTE</div><div id="QUOTE">Treatment
If a ganglion cyst is symptomatic, it can be managed by aspiration or excision. Aspiration of the cyst is the simpler of the two procedures, but cysts recur in approximately 50% of cases. With surgery, the recurrence rate is reduced to only 5 to 10% if it is fully taken out, and complications rarely develop. Recurrence rates are lower when the hand or finger is immobilized for 1 to 2 weeks.
Arthroscopy of the wrist is becoming available as an alternative to open excision of ganglion cysts. During arthroscopy, the origin of the cyst can be seen. No immobilization is needed after arthroscopy.
One traditional method of treating a ganglion tumor was to strike the lump with a large, heavy book, causing the cyst to rupture and drain into the surrounding tissues. Since even the poorest households often possessed a bible, this was commonly used, which led to the nicknaming of ganglion cysts as "Bible Bumps" or "Gideon's Disease." This treatment may be effective, but is no longer recommended, as patients risk damaging the surrounding area. As this may make the cyst worse, other treatment options are preferable.</div>
Hope your local doc sorts it out for you soon.