I Recently Had The Sentinel Node And Three Other Small

I recently had the sentinel node and three other small nodes removed from under my right armpit. I developed a 220cc seroma which was drained by my doctor. Soon thereafter I noticed what appears to be a very pronounced, painful tendon in the center of my armpit going from the surgery site to my elbow running along the inside of my arm between the tricep and bicep. It feels like an elastic cord of pain and is limiting my movement.