Hey,
If you did online payment, than make sure you got a receipt or any notification from the bank regarding the payment. If the payment was made offline, than too you must be having a challan copy. So, if you have any of the above proofs of your payment, then please contact your examination board as soon as possible. If payment has been done properly and recieved by the board, then you can definitely sit in the examination.
Hope this helps!
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