Good advice from everyone. Also you can sit in silence and observe the blockage area. see what feelings it brings up, and try to observe with all of your senses, looking at one at a time such as sight: what color is it, what shape, how big, texture, etc. Do this with each of the five senses.
Be sure you don't try to find reasons or make up stories, just observe. Even though it may be caused by something in the past, it is not necessary to know what it was; only what it is now.