Is it legal to receive money for your own developed software without any company or registration of any kind?

[INDIA] Please help me regarding this query. I'm a Programmer. I made some mobile games. Games i developed are completely my own. They do not infringe any copyrights. However they are registered nowhere. I published these games at Ovi ( a site by Nokia). Games are free but they contain ads inside, & i receive money from an ad-company. I got this information about the copyright from few sites, that moment you made a software, you hold the copyright for that software. But to prove it better in a court, you should register to a copyright office, but it is not mandatory. Please correct me if i'm wrong. Is it legal in India to receive money for these games from an advertisement-company without any company or business registration? If not, what type of registrations should I do? I'm not in a position to set up my own business right now. Thank you very much. Please answer it according to Indian laws.