Hi,
This is a very common feeling to have after cleaning. This occurs because the hard calculus is removed while cleaning your tooth. sometimes this calculus/ tartar when stuck in between your tooth can result in a gap in the tooth. Simply put, the gap occurred because tartar was covering it. Having tartar is not going to help you and can further affect your gums and teeth
Next Steps
You should visit your dentist and discuss the options for closing the gap. There are multiple treatment options available for this and the dentist has to choose the plan thats best suited for you.
Health Tips
Don't worry about this. Yeah from your perspective it can look a little odd, but this can be corrected