Can I take ginkgo biloba if I have got stomach ulcer?

I can't see any reason why it would be unsafe for a completely healthy person. If you take any of a large, large group of different medications that use the same metabolic pathway in the Liver (Cytochrome P450 or CY-450) then they may have diminished function. There is an extensive list here: https://www.drugs.com/npp/ginkgo-biloba.html

Why have you not had the stomach ulcer treated, from my experience ulcers can be nauseatingly painful (but then, I had 7). The stomach ulcer could be caused by something simple like Helicobacter pylori which is simple to treat. Or you could be an unlucky soul like me who gets them from simple stress (clearly not simple but you get the gist of what I meant anyway).

Have a happy holiday season.