Remove any loose paper, prime that area, apply thinned sheetrock mud with a 6" with dry wall knife, roll over it while still wet with a 1/2 nap paint roller. Once dry prime that area and repaint.
This is going to be an ongoing problum. If it was mine I would just wet it down and remove all of it or go over the whole wall with 1/4 sheetrock, or better yet remove what you have there now and replace with new 1/2" rock to make it smooth.