If your J-1 visa is subject to the two-year home-country physical presence requirement, you cannot do any of the following until you fulfill this requirement:
Change status in the United States to a nonimmigrant temporary worker (H) or intracompany transferee (L);
Adjust status (I-485) in the United States to lawful permanent resident status;
Receive an immigrant visa at a U.S. Embassy or Consulate; or
Receive a temporary worker (H), intracompany transferee (L), or fiancé (K) visa.
There is a provision in U.S. law for a waiver of this requirement by the Department of Homeland Security (DHS), U.S. Citizenship and Immigration Services (USCIS). If you are subject to this requirement, but not able to fulfill it, you may apply for a waiver.
Program sponsors generally inform exchange visitors about the two-year home-country physical presence requirement. Exchange visitors are generally also made aware of it at their visa interviews. If you are unsure whether this requirement applies to you or your situation, you can request that the Department of State, Waiver Review Division conduct an advisory opinion for an official determination.
Resource: U.S. Department of State