Ultrasounds results good or bad?

18m

I’ve had a small and firm lump in my chest, above a rib and near the sternum for around 3.5 years now. It is movable from left and right.

I went to my doctor last week and had him examine it, and he said it felt like a little bit of gristle.
He referred me to an ultrasound for peace of mind and I got the results back the next day.

The report said that no mass lesion or fluid was detected, and that all tissue was within normal limits.

I still feel the lump and it feels distinct from the rest of my body/chest. Does the ultrasound report mean that they could have missed the lump?