Hello and welcome,
Any mouth bleeding is always NOT from mouth. I mean the site of bleeding is important. Next is whether the bleeding is severe or mild then i want to know whether it is recurrent or single episode. Even lot things to be needed to come to an conclusion.
Anyway, if the bleeding is very bright red type or fresh type, then as a first aid
measure you can drink few sips of ICE COLD
water or gurgle with the same ICE COLD WATER. Rather put an ice cube if you can see the bleeding point. Local bleeding will stop. If the bleeding is about dark colored red, like brownish black, ICE COLD WATER WILL not help much.
Anyway, In either case you need a through check up, but as a first aid use chilled cold water.
Wish you an early recovery