Welcome to HCM.Unprotected oral sex
carries a comparatively lower risk towards HIV/STD
As your partner told that the thigh rashes could be a jock itch
HIV symptoms can occur, if at all infected, only after 4 weeks and not earlier than that.
So your cold
like symptoms may likely to be due ordinary viral infection that could occur to anybody,especially after a close encounter.
Regarding the dark spot on your foreskin may unlikely to have any clinical importance. Anyhow 24 hours is so early to predict and you must have a close watch over the lesion. If it develops then immediately consult your Physician
Safe sex is always preferred in future.