Here is the thing:
That is a cold sore caused by a variant of the herpes virus usually Type 1
You can get it through close contact. E.g kissing
It lives in the nerves under the skin and the moment you become ill, or your immunity drops, you see them
You can manage it or speed healing
In most cases, it will heal on its own
Always see a doctor.
Avoid kissing anyone who has a cold sore or sharing drink or spoons or even cosmetics like make up
Don't perform oral sex on anyone who has genital herpes
The likelihood of infection is high especially when the sores are visible,
There are a few ways to prevent this, both types
Do not share makeup items eg brushes
PLEASE DON'T KISS BABIES, whether you have this or not.
Always practice safe sex, protect yourself and others.
There are some drugs however that your doctor will prescribe to help speed it's healing if you have a bad case