What do you put on a ganglion cyst for treatment? ice?

Not much: Unfortunately there are no topical treatments for ganglions that I have found effective. You can try an aspiration where a needle is inserted into the ganglion to remove the fluid. If it continues to cause symptoms you can consider a procedure to remove the ganglion.

Nothing: Splinting the joint and the use of anti-inflamatories has the best chance of getting the ganglion to receed in size and posibly reduce any pain.

No ice: If in fact you have a ganglion cyst, this is a fluid filled sac communicating with the joint. Ice helps with inflammatory issues for the most part. A ganglion cyst is not an inflammatory condition. Once the diagnosis is confirmed it can be left alone, aspirated, or excised. Best of luck.