yep you can close back up, Your cervix is a spincter and if you get nervous or anything it can close up. Sounds like you are getting ready though and watch if your water broke! Take you temp and no baths etc.... It should happen soon but if you do not ahve a fever and your not contracting regualr then you can wait for it to happen. There are actually 2 layers of the water bag and they can have holes in seperate places and leak but it is nothing to worry about unless you develope a fever.
It sounds like you are in the beginning stages of labor. I had the same thing happen to me with both of boys... as a matter of fact, I was 3 cm dilated with my first and having contractions regularly and wouldn't admit me until I was 4 cm or my water broke. Well they sent me home about 9 pm and I was there the next morning at 4 am because my water broke. It is possible for you to go from 2 to closed but it means that you will probably go pretty fast in the beginning since you have already been dilated already. I would say keep count of your contractions (time them) and write them down and see how far apart they are and how painful. I also recommend walking around which can also make you dilate more... Best of luck to you!