بسم الله الرحمن الرحيم
Was any amount of mahr fixed at the time of nikah or not? If it was fixed, then you will have to pay the same. And if no amount was fixed rather the nikah was done without the mention of mahr then both of you may fix the mahr whatsoever you wish. If both of you fix less mahr with mutual consent, then you should pay it, since you have paid one thousand rupees with the intention of mahr, now you may pay the remaining portion. It is better if you pay at the earliest, though it is not sin to delay in paying the mahr in the question mentioned above.
Allah knows Best!
Darul Uloom Deoband
This answer was collected from the official ifta website of Darul Uloom Deoband in India.