I know it says Dry Clean Only but can't I....?

Oh, leather cannot be washed, and especially with ammonia, which is what is in Windex. And if it really is a vinyl, that still would be a problem using Windex - that cleaner is just too abrasive. Get a good liquid leather cleaner and conditioner and use it over the spots doing it multiple times if you have to. You could also use Murphy's Oil Soap without adding water to the cleaner. Don't just clean the small spot, make sure you cover a larger irregular shaped area so you don't end up with a big polka dot. When you've got it cleaned, then clean and condition the whole jacket.