A Bleeding Growth on a Young Shih Tzu's Lip
Small growths on the lips and in the mouth of young dogs are often warts (papillomas), which are caused by a virus and usually go away on their own. A skin tag or another type of growth is also possible, and lips bleed easily because they get bumped and chewed. That doesn't by itself mean it's serious.
To stop the bleeding, press gently on it with a clean, damp cloth for a few minutes. Try to stop him pawing at it, and give softer food and toys for a few days. Don't cut it, tie it off or put anything on it.
Any growth that bleeds is worth having a vet look at in the next few days, so they can tell you whether it's likely to go away by itself or should be removed or sampled. Go sooner if the bleeding won't stop, it grows quickly, more appear, or he has trouble eating.
See warts and skin tags on dogs.
This is general information, not a diagnosis. Please follow your own vet's advice.