This is an incidental finding and likely to be inconsequential to your health or your medical . Of course your AME now must have the histology to prove it is OK but hopefully this is just passing paper around. There is a small risk it is more serious of course, which is why it needs biopsying, but I really wouldnt be too concerned.
I must say if you paid and went privately I am disappointed the radiologist didnt discuss his findings with you at the time and explain matters rather than just mentioning it in the report (if I have read your post correctly). He could possibly have given you more of an opinion on what his findings suggested. To biopsy this we simply insert a needle under local anaesthetic using the same ultrasound or a CT machine and take a small sample.
Best wishes