is it necessary or not to post a article at indispire in english?i don't know?

You are free to post your article in any language that you are comfortable in. It's just that since english is the popular mode of communication, so one will in all probability get more readers for a particular post if it is in English as compared to one written in some other language. 

There is absolutely no compulsion for writing in English only, one should write in a language he/she is comfortable in. We blog, we write to express our thoughts, our perspective, our opinions. That's the primary idea/intention of our blogging, isn't it? If one is being able to express himself/herself in a particular language better, he/she should continue writing in that particular language.

However like I said, when you write in some other language, you may not get that many readers. If you are okay with that, you can go ahead. Moreover Indispire is no contest. There have been several instances when people have written their entries for Happy Hour campaigns in Hindi and won vouchers.  

thanks a lot sir

You may proceed in Hindi or any other language...