This happens so not to worry.  These spots generally appear when moisture or water has been left on the blade.  It is important when you put your blade away that it is completely dry as are the scales.  You can ensure this by running a non-lotion tissue over the blade and scales.You can use a small amount of metal polish such as MAAS and a polishing cloth to take case of those spots should they appear.   Be very careful as you are holding a very sharp blade.  I would suggest resting the blade into something like cardboard or a towel to prevent it from moving around while you polish it. If you have extensive 'patina' on the blade I would recommend sending it off for professional restoration.