Hey,
First of all, do not worry. Hydrocele is an easily treatable problem. Plus they are most common in babies, and also disappear on their own. You need to worry only if it pains and swelling increases, which is not in the case of your baby. I suggest take an opinion of another doctor whether surgery is really required or not.
Please go through the links below, hope it will help you.
http://www.healthline.com/health/hydrocele#Overview1
http://patient.info/in/health/hydrocele-in-children
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