No, the financial aid packages you receive are not final. Financial aid packages will come at the same time as your acceptance letter. It would be best if you compare packages from the other schools where you have been accepted. Perhaps your circumstances have changed.
It is acceptable to negotiate the medical school financial aid options based on your specific need. According to MSCAR, “Your offer will list various forms of financial aid you are eligible to receive; however, you will need to decide if you want to accept all the aid offered."