Thank you for your question.
Your sore throat
is not as a result of the piercing that was done.
It is most likely because of some virus or bacteria you contracted from someone who also had a sore throat or the virus/bacteria.
May be where you were having the piercing done someone had this kind of infection which was transmitted to you.
I would recommend that you should take over the counter motrin
for this sore throat that you are having. It should improve in due course of time and usually does not require antibiotic.
If your symptoms do not improve or worsen I would recommend that you should consult a doctor because you may require an antibiotic at that stage.