Hi jakkok
You should have applied for Optional Practical Training prior to graduation . The OPT is good for a year. That was my course of action.
"If you are applying for OPT based on completion of all coursework and/or completion of your academic program, you must submit an application for optional practical training prior to your completion date. Applications received at USCIS after the completion date will be denied."
Now that you have graduated, is too late for OPT; And I am not really sure/familiar with the H1B visa options for nurses;the way that I think you can remain in the country is similar to my case after my OPT will expire- is to try and enroll for another degree, extend your F-1 status; meanwhile find a hospital willing to hire and sponsor you for GC. When Visa Numbers become available, you would be able to file for Adjustment of Status and employment authorization. If you decide to go this way and you find an employer, you should also get going your CGFNS Visa Screen Certificate.