New filling has a groove and a tiny piece of the filling fell on the same day.

[tereoli]

hello,
i just got a filling fixed, i found a black spot that was apparently a crack. the dentist fixed it, but when i got home, and before eating. i checked the tooth. in the middle he left a groove that none of my other fillings have. i touched the groove gently, because i saw a piece sticking up, and a tiny piece came off.

should i go back to the dentist? or are grooves normal? theres nothing black showing, and it doesnt bother me. can bacteria get inside?