Bump in 2m thigh

Jacky • 24

My husband noticed a ball in our 2m old thigh under her skin. I felt it and it feels like a lump. Her other thigh is fine and no ball. She got her vaccines a week ago & I was wondering if her thigh was swollen but she got them on both legs and only one has a lump. Should I be worried? I’m def calling her dr tmrrw about it tho. Anyone w similar experiences “?