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.