Circumcision healing and care?

My newborn son was circumcised today and I was able to take him home. When I changed his diaper his penis skin was up. I pushed it back and put a cloth with petroleum jelly over it as instructed by his doctor. He was screaming in pain when I touched it. Should I be doing this? Will it heal normally if I leave it alone? How should I clean it? Will it get infected? Please be specific and give as many details ad possible.