Sadly, you have to bring frets down to its level. You can kinda cheat and have higher action and only level the frets around it before polishing them. (Always crown and polish your frets after filing them. You'll need a magic marker.) I'd have to see it, and the whole situation, to really tell you what it needs. Eventually, guitars need to be refretted. They often need a neck reset after a couple of decades. That's a hell of an ordeal on an acoustic, but can be done more easily on an electric that has a removable neck. If it's a 'set neck', it's also a pain in the ass. It involves removing the 15th fret (often, sometimes a different one, but usually the 15th) and drilling holes into the place the fret was. You then pump steam into them or the new modern method is to use foam cutters that work by melting the foam. You stick those in there, one on each side, and let it heat up - but not burn. When it's hot enough, you work it loose. The glue usually weakens with the heat and you can then remove the neck, sand it, adjust it, and put it back in the right position. That's a whole lot of work and it's easy to fuck it up. That's not something you probably want to do yourself.