You're a size 6, so why on earth did you buy a 5? We're happy to sacrifice our feet for the shoes we want, but sometimes we go too far. So, when "wearing them in" is too painful, here's a shortcut to avoid the pinch.
Put on a very thick pair of socks (or several pairs) and squeeze your feet into the shoes. Then, take a hairdryer and blast the tight areas with hot air while flexing and stretching your feet. Keep the shoes on while they cool down and then check the results while wearing your normal socks or stockings. You can repeat this process several times until you get a good fit. But be aware that too much heat will dry out the leather, so give your shoes a soothing treatment of shoe cream or polish afterwards.
Also, remember that water will make leather brittle so wet shoes should be dried gently, not placed in front of the fire or on top of a radiator. You can speed up the drying and help wet shoes and boots keep their shape by stuffing them with newspaper.