Cold sore treatment

Hello. I previously got a light green liquid from my doctor who said he got while on a trip to Japan. This rapidly healed my cold sore like nothing I've used before. Can some please let me know what this is. Thank you

On the box or tube?

It can be anything. Do you happen to have a photo of the label that you can upload on a random uploading site and post the link here? Was it an over-the-counter merchandise or did the doctor need a prescription　to obtain it? The following images are just for your reference.

https://www.google.com/search?q=%E7%B7%91%E8%89%B2%E3%81%AE%E6%B6%B2%E...

When you say “cold sore,” do you mean something that develops on your lips/inside your mouth, or talking about some throat condition from a cold? Also the liquid - was it something you drink, or was it an ointment/liquid for external use? Indeed a bit more details and an image would help.

If you have a picture of the box or tube we will likely be able to help you, but unfortunately it is not possible to (or safe to speculate) identify a medication based on the color and general appearance.
You may also be able to find out from the clinic, even if you are not there many places at least where I am perform phone consults. Depending on the clinic's policy, the receptionist may also be able to pass on a question to the doctor, if it is just a simple matter of "I would like to know the name of that medication". In fact if it was a prescription medication you can just get a health summary or prescription record from reception. Many people carry a list of their regular medications, so it would not be an unusual request at all.

I just checked, topical antiviral therapy does indeed exist. However, it is only to be used in certain situations, and in certain other situations you need tablets.
Might be aciclovir, might also be something else in the same class of drugs. Might even just be simple anaesthetic or something else. Again, not safe to speculate without actually seeing the box/medication.