Lumps and bumps after lymph nodes removal

I had a mastectomy on my left side and 19 lymph nodes removed, 15 of which were positive for cancer. IV had a bit of pain under my left arm which I was expecting but today whilst mosturising IV came across a lump about the size of a pea half way down my inner upper arm. Just wondering if anyone else had this issue after lymph removal ?

I know  your panic. Also had mascetomy and 17 lymph nodes removed. Then found a lump..turned out to be cording issues.  Got to keep up the exercises! Don't know if you had radiotherapy but it's taken a while for me to fully appreciate the extent of the side effects and how long they can go on!