sore breast update

so I've been to the doctor twice. the first time she said I pulled a muscle in my left chest that went to my back. the next visit my breast was still in pain but I started my period, she felt that my left was lumpier than my right and she said it could go away as my period goes. I had a breakdown and said that I was scared that it could be something that's "serious". she suggested, for the sake of my sanity, go order a ultrasound so I did. meanwhile, as my period ended my breast pain went but I still feel a "knot" or something that's pretty big compared to my right breast. should I still go get an ultrasound?