Just stop using that fake SSN # and you shouldn't face any penalties. Should you continue using it, however, you could be placed in deportation proceedings and your story could be hard to swallow..
I agree with Mr. Behar.
Please be advised my answers to questions does not constitute legal advise and you should not rely on it, due to the fact that we have never met, I have not been aprised of the facts in you case nor have I reviewed any documents.
I agree with the other answers. Now that the issues is known, do not continue with the same SSN. Additionally, you do not indicate your current immigration status. If you are legally eligible for residence/ employment in the U.S. and have been since you began working, you can probably request a new SSN from your local Social Security office and also request that your earnings record be corrected to show the change. However, you will want to consult with an immigration attorney first if there are any questions about your legal status. It is worth a small investment to make certain that you are doing everything "by the book."
This response is based on the limited facts presented and is not intended to substitute for direct legal advice, nor is it intended to establish an attorney-client relationship. It is intended to direct you to issues which you may desire to explore further.