How Long Does The Wound Take To Heal After Pilonidal Cyst Surgery?

My son had pilonidal cyst surgery. The gause packing and stitches were remived after two weeks and the surgeon said everything looked fine. After one week the surgeon said the wound had opened and looked weepy. He removed the remainder of the stitches, but said my son may need another surgery. One week later the area is still not closed, but there are no signed of pus. He is keeping it dry. What is the time length for healing of a wound of the degree. Thank you