That triangular tissue is the interdental papilla.
It may or may not have been damaged by the agressive flossing
There is no "dental glue", but there is something called a periodontal dressing which can be molded and placed over the wound to protect it from further trauma for the next few days.
Since it is in an area that is quite visible and esthetic, you should have it looked at by your dentist since loss of that papilla could result in a black triangular space in that area.
...A doctor will see you now ›