Advice on my 2 year old sons winky please answer

So today my little boy has been ill he's had diarrhea and it's caused all his nappy area to become inflamed. The trouble being he's swelled around his penis and this has caused the skin to retract exposing the tip of his penis. It doesn't look red just swollen. Has anyone's little one experienced this before if so can they advise me on what to do as the doctors just told me to put cream on and watch it for a couple of days