Seeking: Indian Tax Advice

What do if someone is not giving his PAN details for TDS but I have already transferred some good amount of money to his account? I only know his name and account number and didn't knew about this TDS thing before transferring.

You sent $100k to somebody in India to buy Virtual Currency and you have no idea who they are? Haha lol
This sounds very suspicious.

http://www.incometaxindiapr.gov.in/incometaxindiacr/ppt_html20081017/TDSTutorial/TDStrial2.html
http://business.gov.in/taxation/tds.php
http://taxguru.in/income-tax/tds-legal-service-received-india.html
http://lmgtfy.com/?q=TDS+india+legal

Yeah, that's my BAD I admit it. I had no idea about TDS, I thought if am transferring it through bank transfers, its their headache for what to show this money and not mine.

Well if you are in the US, the bank will also notify the IRS of the large money transfer (I think) and you may have other Tax issues.
You probably need EXPERT advice from a Lawyer/Accountant that specializes in this sort of thing.
I would be wary of the advice you receive on the forum when discussing that amount of money.