Is it necessary to write an introduction post???

No. It is not. However, it is considered as a good practice.
I agree that there's some paradox here. You need to write most important post (first impression, right?) at time, when you are least experienced in using that platform. That could be scary, but introduction post have many advantages:

• You are an expert in this subject
• No one ever wrote about it before
• With some luck you might pass a Turing test ;-)
  etc.

By the way, you missed a chance to include kitten photo in your introduction to make it more appealing than just steemit logo :-)

Anyway, welcome to Steemit! :-)