To dream that you have a blister implies that you are wasting your efforts on a rather insignificant matter. Pay attention to how the blister formed. To dream that you got the blister from manual and hard labor means that you aren't trying hard enough to resolve minor issues. To dream that you got the blister from a burn indicates that you are experiencing trouble in a relationship.
Notice where the blister appears. If the blister is on your hand, then it implies that you are struggling with control and authority. If the blister is on your face, then it means that you are experiencing problems with how you view yourself. Perhaps you are feeling inferior or unaccepted.