Hi.. Presence of tampon inside can increase the chances of infection.. It would be ideal to know what type of infection and a how serious the infection is by an examination.. But alternatively, there are a few home remedies for certain type of yeast infection.. So if you are sure it was a yeast infection then such home remedies can help.. Some of the home remedies are use of tampon soaked in vinegar, or boric acid suppositries.. And remember to remove the tampon after few hours..