Please help

I have a lump under my left armpit for over a year that seems about the size of a walnut, it doesn't seem to have gotten bigger, but it's deep in my armpit and it's kind of hard to tell. It doesn't hurt except when I push on it or squeeze it, then it hurts all around my armpit sometimes for several hours afterwards. It does seem to move around but kind of hard to tell. You can't see this lump by looking at it, but it can be felt. I went to the doctor on this, at first he couldn't feel it, but after a few minutes he said there was nothing to it.  Should I be concerned with this?

[islandgurl]

I would find another doctor.  I would ask for an ultrasound of the armpit area.  I have a lump that's not quite in my arm pit, had a mammo & ultrasound on it in June, went for a re-check with dr today and am having another mammo & ultrasound next friday.  Dr. doesn't think it's anything, but I did ask for a biopsy on it to be sure.  He will that after next mammo & ultrasound next week.  I would rather just know for sure that it's nothing.
Good luck.