Other than an educated guess based on how it looks there is no way to know the age of the scratches. I tend to doubt that they are old healed scars because I doubt a frog that was injured badly enough to leave scarring of that degree on the head region would survive the wounds. It looks more like what I call "paint scratching" where the frog gets the colored part of his skin scraped off usually by leaping against something. Such light scratches look just like the pictured frogs and will heal over in a few months. As far as medication for the wounds it shouldn't be necessary no deeper than it appears to be. It should heal on its own.