[Ike]

Hello,
Recently, I had sex with my partner and while we are both STD free, I believe maybe there is a possibility of me contracting some sort of STD This is my dilemma. On my right shoulder right above my armpit I broke out in some sort of rash which is red, sore, with puss, and quite itchy. I do remember that the evening before I scrubbed this area while in the shower which could have open skin revealed. Then when my partner finished oral on my he kissed me on this spot. I've cleaned it with alcohol swabs, put some antibacterial ointment it and have bandaged it so it won't spread unknowingly. I have no other apparent or visible signs of STD's anywhere on my body.
But what could it be? Could it possibly be an STD. Can an STD be appear on such an area such as this?
Please help me.
Thank you very much.