First off, congratulations on being accepted! You are one of the few that were accepted so I would take that as a compliment.
There are probably a lot of people wishing they were in your position where they were accepted into school, but in the end I understand you have to do what you think is right for you and where you feel most comfortable.
Don’t make a decision you are going to regret later in life, if you want to do premed do it, but if you want to do nursing do that! If you do give up your nursing spot then it will become open to someone else that knows they really want to be a nurse.
I know it's going to be a difficult decision, but good luck to you on whatever you decide.