Suggest Remedy For Itchy Rashes On Scrotum & Penis

My 2 year old son has a rash on the inside folds of his legs (near his scrotum and penis, where the edges of the diaper are around his legs) I thought is was diaper rash and have been applying the diaper rash cream, but it's not going away. Today I noticed he is trying to scratch at it so I think it has now turned itchy as well. The rash is red and sort of patchy white.