There are some possible ways to fix a nano titanium stainless steel sink if it is scratched. Here are some of the methods I found:

You can use a commercial scratch remover, such as Bar Keeper’s Friend, to buff out light scratches. Apply a small amount of the product to a microfiber cloth and rub it gently back and forth across the scratch, following the direction of the grain. Then, wipe with a fresh cloth to remove any residue.

You can also use a baking soda and water paste or a non-gel whitening toothpaste to fill in and smooth out light scratches. Apply the paste or toothpaste to the scratch and rub it with a microfiber cloth in the same direction as the grain. Then, rinse with water and dry with a clean cloth.

For deep scratches, you can use wet 400-grit sandpaper or a coarse scouring pad dipped in olive oil. Rub the sandpaper or pad over the scratch in one direction, following the grain. Then, switch to a finer grit sandpaper or pad and continue buffing until the scratch is less visible. Finally, wipe down the sink with a microfiber cloth and some oil to polish it.