Hope you are doing good in this pandemic situation. Let me get straight to the point that you have chances but the chances are very low. You mentioned the closing rank and you are very close to it. Usually students choose to study BSc math at BHU when they couldn't get a medical seat or engineering seat, but it's very probable that some person may leave a seat if he get a medical or engineering seat therefore you have chances.

You don't need to worry please be patient. You have chances of getting your preferred branch.