I would just bathe your feet in a warm water with a little salt added, dry carefully and put a thin layer of antiseptic cream on the blistered area. Just wear a pair of loose socks if you need to tonight (assuming you are staying indoors) or backless slippers (mules?). If you do have to go out, put a plaster over the blistered area and wear some different shoes (with socks if you can to help protect your heels). When your heels have recovered, you might want to just wear the new shoes indoors or only on short jaunts out, to break them in.