Is the lymphedema on the same side as the pain? I had a unilateral mastectomy five years ago and have lymphedema on that side. Periodically I get sharp pains in my arm pit. My lymphedema therapist told me that when we use the lymphedemetous arm we are using far more energy than we expend using our other arm because it is filled with fluid. I think picking up something heavy (and it doesn't have to be that heavy.) can cause pain on that side if that's the side you are getting the pain. Another thought is I don't know how deep the tumor was. For me the surgeon had to go through several layers of nerves. I sometimes get shock like pain. It's fleeting. Nerves heal very slowly. My oncologist said it is very common and unfortunately it doesn't completely go away. If it doesn't get worse, December isn't that far off. Be sure to ask your oncologist.