Warm compress. A stye is caused by a blockage of the oil glands on the eye lid margin. It will cause redness, tenderness, and swelling in the area. Usually you will want to start warm compresses to the area 2-3x/day to try and reduce the swelling and help with drainage. You should see your pediatrician for confirmation as there are other causes of eye lid swelling.
Stye. Bening. Do warm compressors for 10 minutes, 2-4 times per day (very carefully with the warm towel), do eyelid shampoo with baby shampoo. If getting bigger, see ophthalmology.