looking for advice...what should I do

This might not make sense but I was just looking for some friendly advice. I have(had) been out of work for about 6 months. I applied and interviewed for a job I was interested in but didn't hear anything for a while. Then I interviewed for a job I thought I could be interested in and accepted the position. While in orientation (classroom stuff) I received a call and was offered the job I was interested i first. I thought about it but felt I was obligated to stay with the position I was orienting for. And since it was in the same hospital system I thought I had to stay 6 months before transferring. Now I have had my first day of orientation on the floor and I can't help spending time thinking of the job I turned down. I wish I had did something before. I am not sure it is "right" to inquire to that supervisor about the job opening and I am afraid of letting my current supervisor know anything about it. What should or could I do? I think part of my "anxiety" is just starting at a new place and a new field after beiing out of work for a while. But I cant help thinking about the position I turned down. Sorry this got so long. Thanks for any advice!