Thank you for posting your question here, I will try to answer it to the best of my abilities.
Truth be told very few doctors have experience in this kind of thing, usually doctors who work on resorts know alot about these things of occurrences.
From what I can tell the doctor pulled out the sea urchins splinter (not sure what its called). If you are worried about the blister
I recommend you see a dermatologist
, as they may some idea on how to go about with this event.
It is also possible that the blister and the seaurchin pricking your toe event are totally unrelated.
I hope I managed to help you