A little experimentation with various solvents shouldn't harm the tile, though you may want to avoid the grout lines in case they might get discolored. I'd try some brush cleaner or paint remover on a rag and rub the spots with finger tips. Even mineral spirits might do the job if the tung oil isn't fully cured.

Formby's Tung Oil Finish is (not tung oil at all) but a thinned alkyd varnish. You don't say if your ceramic has a glossy coating or is porous. I'd carefully scrape off with a single edge razor blade and if any remains, lacquer thinner or acetone on a cloth. If you don't have either of those solvents, a little fingernail polish remover should work. Mineral spirits will not work it if it has cured at all.

http://www.popularwoodworking.com/techniques/finishing/oil-finishes-their-history-and-use.

I will try the razor blade and lacquer thinner. Thanks