OT: A dental question

[veggieburger]

Hey dentists. My 2.5 year old just got one of her 'molars' in (not sure if it's an actual molar...it's a back tooth.) Up until last week there was still a tiny flap of gum on it, now it has pushed through. The issue is that there appears to be a small dot of vascular tissue in the center of the molar.

It doesn't affect her chewing (she chews both sides) and otherwise there's no issues....except when we brush. She says it's "owie". Could that be a cavity? Or something else? I'll try to snap a picture, but it's not easy.

Thanks for your help, really.