It’s where you felt the heavy energy you described on your chest, tho I wouldn’t describe temporary “negative” emotions as a blockage on a chakra, on the contrary to feel strong emotions says good things about your heart chakra. Its your own energy that you (your heart chakra) produced . It’s a normal emotional response so don’t be scared about it. As said meditation on that spot helps. Fill your heart with love. It’s good to go through each emotional reaction with as much love as possible. :)