Hi asheshayushmishra,
First off, a 630/Q47 is a pretty good score (it's just a bit shy of the 80th percentile overall), so it might be enough to get you into your first-choice Business School, especially if you have a strong OVERALL profile. That having been said, many Test Takers spend 3 months (or more) on their studies before they hit their 'peak' scores, so it's likely that you just have not put in enough time and effort yet.
Before I can offer any advice, I'd like to know about how you've studied and your timeline/goals:
1) What materials have you used during your studies?
2) What is your overall score goal?
3) When are you planning to take the GMAT again?
4) When are you planning to apply to Business School?
5) Do you know which Schools you plan to apply to?
GMAT assassins aren't born, they're made,
Rich