My dentist pointed this out and doesn't have a clue what it is

[ConcernedMomOf4]

Hi! I took my 2 year old son to his dental check up yesterday (2 March 2021) and, his dentist pointed this out to me. I brush my sons teeth daily, twice a day and have failed to notice this. I have looked on google with the hopes that I may find an answer but I have failed to do so. The first image is the best depiction I could find online pf this anomaly. The last two images are of my sons bottom right canine tooth.
Honestly, as a parent you never want a professional to say they don't know what something is in regards to your children, however that is exactly what he said. "What the hell is that?" Hearing him say that sent me into a panic attack whilst I am trying to soothe an overly fussy toddler who has people sticking their fingers in his mouth. So, someone. Please help me.
It doesn't seem to be bothering him at all but now that I know it is there its bothering me!

 

[Dr M]

Good day

This is a very interesting case, and to be honest, I am also not exactly sure what to make of that. Maybe an x-ray would give more information regarding the structure of the tooth and bone underneath the gum, and that can give you a better idea as to what this is.
It almost appears like calculus or mineralized plaque in this area. Has the dentist tried to remove it with a scaler? If it can't be removed, it might be a good idea to consult a pediatric dentist.