What the hell is a gum boil!?!?
A small boil or abscess on the gum
That wouldn't just pop up in a couple of hours though surely?
It is probably a real blister as a reaction to the caustic alkaline solution from the Bicarbonate.
No, you should not use it directly silly girl.
Use "Bonjela" or similar to take the sting away and drink cold non-fizzy drinks.
Alternatively, you have Foot and Mouth.