Yes it's OK to put rubbing alcohol on a cold sore.
Rubbing alcohol is a good way to get rid of cold sore and helps kill bacteria on the cold sore as well.
You can soak a cotton ball into some rubbing alcohol and apply it to the cold sore 2 to 3 times per day.
The rubbing alcohol will help dry out the cold sore and help reduce the swelling of the cold sore as well.
If you apply the rubbing alcohol daily the cold sore should begin going away within a few days and after a week the cold sore should be gone or almost gone.
Toothpaste can also be applied to the cold sore to dry the cold sore out but rubbing alcohol will work as well.
You can apply a cool compress or an ice pack to the cold sore as well or use some apple cider vinegar to get rid of the cold sore.
But if you have rubbing alcohol it's one of the best ways to get rid of cold sores at home.