Thanks for posting your query at DoctorSpring.com
I think it could either be a flare up of vestibulodynia or a new infection.
Get a vaginal swab done to rule out infection.
Avoid using new products on the area, as it is so sensitive.
In fact, use nothing.
Just clean with water.
Avoid irritant fabrics for intimate wear, stay off talcs, scented toilet paper, detergents, cleansers etc.
Use water as a lubricant during sex.
Get your partner screened for all infections.
Use an ice pack for the burning.
Local lignocaine gel which is a local anesthetic can help to control pain, please discuss this with your doctor, and the use of oral carbamazepine also.
Please feel free to discuss further.