Why do you think it blistered? Was the texture dry when it was painted?, excesive dust, was it primered? You can take a 6" taping knife and scrape the blisters off, repair with joint compound(may take a couple of applications, don't build up the compound, but apply it, then swipe one smooth, firm stroke down,) wet sand with a damp sponge(being careful not to remove all the compound, around the edges is good and lightly overall if it is applied smoothly), re-texture to match.