Hi I Have A Penis Rash (on The Head Of

Hi I have a penis rash (on the head of my penis) and it started off as redness but now there are distinct red spots but it isn't an STD because I have not been sexually active. It's been about a week and although I thought the rash was going away it turned into these spots (or sores) - looks like one of them is slightly light yellow with a red border. I was recently on antibiotics for bronchitis (amoxil) and was also taking prednisole. I'm not sure what the rash is and how it can be treated. I am washing my penis with an antiseptic and using Vicks cream to provide it some relief. Is it an infection. What do I do to make it go away? Please advise.