Hmm, sounds to me like the needle went in too close to a nerve. Nurses have no way of really knowing if something is close to a nerve, since IV insertion is done by feel and sight (which is why I am not good at it anymore). Veins are located by sight and palpation. Having an IV close to the thumb is a bit unusual though.

Hopefully it will remit after a while, but it is likely NOT PN, rather related to the IV insertion or medication that you got put in there.

Hope you feel better.