Strange Bumps After Brachymetatarsia Surgery

i recently had surgery to correct brachymetatarsia. about 3 months after the surgery, a hard, knotty bump formed at the base of my surcical scar. it feels like bone and it is very sensitive. my parents told me it was probably a piece of the stiching that they didn’t pull out and it would surface and come out on its own. I have absolutly no idea what it really is. has anyone else had such problems?