I have similar case with you, but on knee, not paintful if never tough it.
I consulted Dr. Au Ting Wah Tel: 392 9297. He tried to use 針筒 to absorb such liquid out but failed because small size (like peanut).
So he also said that only operation can remove it. But as it is not paintful, he recommend me not to take operation at this stage if it never grow bigger.
Thank you for all your replies. I just couldn't wait and had seen Dr. Cheng Chung Lun in Mongkok finally before reading your messages. He said that my case (a 2cm ball-like thing on wrist) is due to the mis-use of efforts (揍bb) and need to do an operation 2 weeks later. ;-(