Hello & welcome
Don't worry you have gingivitis
so you are feeling itching & swelling in your gums.
You have to maintain proper oral hygiene
, start doing warm saline rinses 2-3 times a day, chlorhexidine
mouth wash twice daily, & massage of your gums with tannic acid
gum paint, you will start getting relief as you said that your sinusitis is also subsiding.
take care & thanks.