i attended a clinic yesterday in London for hiv test
I don't believe this is a possibility.
Hello dear, welcome to Ask a doctor's service. I read your query and here is my advice.
I don't think this is a possibility because a nurse that works in a laboratory where HIV is tested the sterilised and one usage needles are the first thing she should keep in mind.
I don't believe that this thing could have happened. Possibly you were distracted by something or just missed the moment when the nurse opened the new needle.
I don't think you should get retested.
If you decide to get retested you should wait for four weeks before redoing test.
Hope I have answered the question. Let me know if I can assist you further.