Hello there.
There are two possibilities.
One is irritation and inflammation of the skin due to tampoon use. In periods, prolonged application of pads/tampoon can cause the skin to be inflamed and sore. This is more if you do not change the pads frequently.
The other possibility is a
fungal infection. These occur more during menses due to pH changes of vagina. Also improper hygiene and constant wetness can predispose tho fungal infection. It usually presents with
severe itching, curdy white discharge and
redness, soreness of the vagina.
So kindly consult a gynecologist for a local examination and treatment.