Many Lenovo A7000 users have reported the issue with the touch malfunctioning. There seems to be a hardware issue. For some users, the issue creeps intermittently, while for some it is a permanent problem.
You may try the following methods
1. Remove the screen protector and check the area concerned.
2. Run the software update to check if any updates are available. If new software is available, update your phone to the latest software.
3. Factory reset your phone. Do not forget to backup all your personal data before doing so.
4. Down load the Lenovo Companion app from Play Store or from the link https://play.google.com/store/apps/details?id=com.lenovo.serviceit&hl=en)
Check the affected area with the Screen Test option in the Lenovo Companion app.
If all these methods fail, you do not seem to have any other option than bringing your device to service centre. If the screen needs replacement, it should take anywhere between 15 days to a month. Since your device is just three months old, you should get it replaced/repaired under warranty.
I could find that a Lenovo service centre exists in Tuticorin. Please check for the authenticity as it was not from the official website.
106, Kasi Nadar Complex,
H VVD Main Road,
Ph - 8754599289