Fake reliving letter submitted to move ahead before FNF from old company

Hi all, I was working in one small organization and I got an opportunity in big MNC. I got resignation confirmation mail from small org. But big MNC was asking for same thing in company letter head. After lot of discussion my old company said that they can't give any thing written in company letter head until FNF will be done. But I was relived from that company so I created fake resignation acceptance letter and I submit there in new org. After join in a week I got a mail that the resignation letter you have provided is not accepted by your old company and they need my justification.
I am very afraid what to do, I can leave the company but I don't want any legal issues. I don't know what to do ? I am thinking to stop going there , I will make some excuse that I am unwell or something. If they want they can terminate me but I don't want to involve in my legal issue.
Please suggest me what to do quickly.

Don't worry they won't go legal. Just explain them the whole situation.It will help. If you got the relieving letter now submit it.

Dear,
Please check if they (current employer) allow you to submit/present Resignation email (acceptance confirmation mentioned) from your Small org.
Sometime better to explain present/real situation instead of creating fake sketch.

Hi all ,
Thanks for your suggestions,
I don't think I have any option to explain anything.the day I got the mail from bgv team that it's a fake doc. and I have to give explation. I was so scared and I stopped going there . It's a 3rd day and till now i did Not got any call or mail from that org. Even now I am also not feeling good to rejoin that again.
I am looking for another option all I want to know that after my this incident. Can they put my profile in black list .. I am eligible to join another org. Is there something like that if i will be blacklist from that org. I will not eligible for any other org.
Can they take any legal action against me because i m not going to the Office after that.
Please advise me .