Chalazion is a cyst in the eye lids due to chronic inflammation of one of the glands and pus becomes thick and it normally does not come out unless a small operation is done to drain it.
It can burst or disappear on its own if you leave it long enough usually 6 months or later. Hot fomentation does neither help to grow smaller or bigger neither do any local antibiotics.
If you cannot wait, get it operated but as the child would need general anaesthesia for this operation. This is a 2 minutes minor operation.