First, you need to see a paediatric surgeon to affirm it is really hydrocele. Once it's been confirmed, surgery can be deferred until the child is a year old, and it's possible for the hole to have closed up by itself.
Kindly, visit a paediatric surgeon and let a proper evaluation be done.

A hydrocele is a painless buildup of watery fluid around one or both testicles that causes the scrotum or groin area to swell. This swelling may be unsightly and uncomfortable, but it usually is not painful and generally is not dangerous. Although hydroceles are common in newborns, they can also occur at any age in later life.

The cause of most hydroceles is unknown.
Hydroceles in newborns may mean there is an opening between the abdomen and the scrotum. Normally such openings close before birth or shortly after.

Hydroceles that appear later in life may be caused by an injury or surgery to the scrotum or groin area. Or they can be caused by inflammation or infection of the epididymis or testicles. In rare cases, hydroceles may occur with cancer of the testicle or the left kidney. This type of hydrocele can occur at any age but is most common in men older than 40.