"Wrong diagnosis"

My 1 year old son had a rash around the genitals, it did not look like a nappy rash, so I seeked for the help of professionals. He also had temperature of 39.2. Doctor said that it is a nappy rash, even though it was more spots than the rash. Than because he had a temperature doctor decided that it may be a virus but wasn't sure what kind of. He prescribed 2 large bottles of antibiotics and a steroid cream to apply on problematic areas. I checked the insert of the cream and it clearly said that it is not suitable for broken skin, and the spots were open, which means the skin was broken and could've got worst if I was applying it. Also he said I should apply Sudocream on the top of prescribed cream. The nurse immediately gave some Calpol and the temperature went down quite quick. I'm glad I decided to book an appointment with GP before I started the prescribed treatment. GP's diagnose was, that it is hand foot and mouth decease and no treatment needed for it, as it will naturally go away. She was shocked to find out about prescribed antibiotics and the steroid cream that could've made my son feel worst after totally unnecessary antibiotics course and the steroid cream.