Hi  sir....    Sensitivity is not related to thulsi leaves chewing.... It is due to damage to Enamel layer which expose underlying dentine... Enamel damage is due to dental caries,attrition of enamel,eroaion,abrasion due to faulty tooth brushing technique... Dentin layer is very sensitive which has dentinal tubules contains free nerve endings....

Stop chewing tulsi leaves. It may alter the taste of your mouth. Sensitivity is not caused due to it. If you have a habit of chewing on food really hard, then after some time the enamel over your teeth will get eroded causing, exposing of the underlining layer of tooth i.e dentine. Dentine has numerous tiny tubules which has sensory nerve endings, which gets irritated when it comes in contact with cold or hot water/tea and even a blow of air may also cause you this pain. This is sensitivity. For now use Thermoseal RA tooth paste twice a day. ( take a pea size toothpaste on the brush apply it on the affected area keep it for 2-5 secs and then brush). Colgate sensitive pro relief mouthwash twice a day . Will also help you in reducing the sensitivity. Do visit your near by dentist soon.