Hey Ritu,
I know, finding a perfect domain name gets tough at times. In your case, you can do the following things :
1) Think of different domain idea: It is always better to get a new domain name, rather than fighting for the already established name. The reason is, you will first have to put in the efforts to make people (who already knew the existing domain name) forget about it, which is not 100% possible. And then create your identity.
2) Buy a domain from the current owner :
Still, if you desperately need the same domain name, then you can approach to its current owner and ask him to sell you. This can be a costly method.
3) Wait for it to expire :
In such a case, you need to be very patient and wait for a domain to expire. So that before renewing you can buy it.
The choice is always yours.