Very dilute solution of Peroxide perhaps? (test it out somewhere that is going to be painted first).
If you can't get rid of the stain (and you are going to put glass on your table anyway), you could think about putting a good quality Irish Linen underneath the glass. What they call a 'tray cloth' would be a handy size.
I can't think why your post on glass for the table was locked, where else would it go except homes & gardens...anyway to answer your post - contact any local glazier firm.
They will be able to cut a sheet of glass to go on top of your table; tip - get them out to measure the table and ask them to deliver it also. If your table is about the size of the one in the photo, I'm guessing you are looking at something around €150, but it's well worth it to protect the table top.