An African lady gave me a blow job and I gave her oral sex and anal rimming about 3 weeks ago. For the past few days I feel there’s a vein that feels like a cord wrapped around my penis just under the head of my penis where the crease of the skin is, also the skin on my penis is dry and after I have sex I have terrible itching in my penis. Not sure if these symptoms are related to the encounter. Also could me rimming her cause me and diseases or infections

Welcome back to the Forum.  Each of the encounters you describe were virtually no risk for HIV and very low risk for other STIs.  It is statistically unlikely that she has and STI and if she did, it is unlikely that she transmitted infection to you.  The symptoms you describe do not suggest and STI.  It is normal for veins to be present on the penis and itching is not a sign of STI although it may be a symptom of dry skin particularly if you've been putting anything on it).   I would not be worried about an STI and do not see a need for testing.  If the symptoms persist, you may want to see your own doctor or a dermatologist.  EWH---