Your F1 is no longer valid as soon as you got approved for H1B. Now, even if you go back to nepal and try for F1 again, you may not be able to get into US because you have to show the consular that you will be returning to Nepal after you finish your study. But, you were already in H1b status, that means you are in a path to becoming a resident, which brings a conflict. So, if you go to Nepal, make sure you have a valid reason / ties that you'd have to show to the consular to support your statement of returning to Nepal after your study. I believe, you may also able to trasnfer h1 status to F1 if you can show that you were in valid H1B status, for which, you may have to present 2-3 recent paystubs etc etc... Good luck.