Investing in a heat gun would be the best solution. Even if a hair dryer does get it hot enough, the slow heating will make the whole area shrink. The beauty of a heat gun is that it lets you put the heat in the exact spot you want it then pull it away. When I have a wrinkle near an edge like that, I aim the heat gun away from the seam and bring it in very close just for a split second, then pull it away. It gets the covering hot enough to shrink only when I point it, but doesn't ruin the seams. If that doesn't fix it, I stay a split second longer the second time.