It would not be easy to get herpes on the chest, actually. The skin there is pretty thick and if there was a break in the skin, maybe, unlikely but maybe, but if the skin was intact, I really don’t think so. And you aren’t describing anything that really sounds like a herpes lesion to me. I’ve not seen any herpes lesion that looks pin sized.
So you were almost 6 weeks out from the encounter when you tested for HSV? I really don’t think you need to test again but if it can set your mind at rest, you can. It should be 16 weeks out from the last encounter that concerns you.
By the way, syphilis tests become positive between 9-90 days out. I don’t think this is syphilis either, but just wanted to get the timing clear for you and others that might read this.
I’m not sure about psoriasis in this case – just don’t have enough info about your situation or from my perspective, I don’t know much about that condition in general.