Had Intercourse. Took Plan B. Feeling Numbness In Vagina. What Is Wrong?
First of all, PlanB should be taken within 72 hours of unprotected intercourse to be as effective as it claims (>90%). Studies have shown that it is very effective for an even longer period of time, but given that you were at 72 hours, you should assume that there is still the small chance of pregnancy. So do a pregnancy test in 1 and 2 weeks from now to be absolutely sure.
With regard to your question, I would not associate the vaginal symptoms that you are describing with the Progesterone in PlanB. Especially given how quickly the symptoms started and given that an allergic reaction to an oral medication is unlikely to manifest as vaginal symptoms.
It might be that you have a vaginal infection, such as a yeast infection. This could easily be evaluated in a clinic setting. It would also be a good idea to have screening for sexually transmitted diseases if this is indicated. If I were counseling a patient like yourself, I would probably have them come in to clinic if the symptoms persisted into tomorrow.
From what you are describing, it does not sound like anything is necessarily wrong with you - just go get checked out if the symptoms persist and definitely heed my advice about the followup pregnancy tests.
I hope this answers your question. If you have more questions, please ask. If you are satisfied, please take a moment to leave feedback! Good luck!