Hello komal

Even if you will not be able to modify choice in second round then you will be alloted college on the basis of choices that you have made in first round. So you don't have to worry regarding this, you will definitely be allotted a college if you would have made choice according to your rank and choosen college which you may get on that rank. 

Good luck for your counselling procedure :) 

Feel free to ask if you have any further queries.