Hello and welcome to hcm,
The damaged tooth in between the sinus
has to be extracted based on the involvement and severity of sinus condition.
You can visit an oral and maxillofacial surgeon regarding this.
Also get the other treatments done.
Maintain good oral hygiene
Use soft-bristled toothbrush and desensitising toothpaste to brush your teeth.
gET your teeth cleaned since chance of gingivitis
is high in your case.
Include vitamin-c rich food into your diet.