Your case has to be seen in two angles. Criminal proceedings for bouncing of cheque and secondly, will it attract any civil liability to pay damages.
Firstly, you write a letter to the seller informing him that you are not interested to purchase the flat, as such, you advised your banker to stop payment. Mere bouncing of cheque itself is not an offence. There is no legally enforciable debt which is payable to the seller as you are withdrawing to proceed with the deal.
Secondly, basing on mere payment of token amount without execution of agreement of sale, awarding of damages is difficult. But, without lapse of time you shall inform the seller that you are not interested to purchase the flat showing the reasons in clear and acceptable manner.