Achy breast

NTS

I finished chemo last Oct but still get herceptin every 3 weeks. I had a lumpectomy in November, additional surgery to clear margins, then finished radiation in January. I had my most recent herceptin infusion this past Friday 5/17. My breast (on the cancer side) started aching the next day and is still aching three days later. Wondering if this is normal or should I call my onc and ask? It’s a very dull ache, not painful just worrisome. I am also taking tamoxifen, and have noticed no side effects from it so far.