For the hitting low part, just adjust the rear sight elevation up to the next increment (200, 300, etc). Several of my Mausers are on the 200m increment to hit dead on at 100m. Since K98's were zeroed with 196gr ammo, your choice of ammo will effect the POA. You could also replace the front site blade but adjusting the rear sight is easier.
As far as the windage, the easiest way is to get an SKS sight adjustment tool. It will allow you to incrementally drift your front site to wherever it needs to go. I think Marstar has them. If it is shooting right, you will need to move the front sight to the right as well to correct it. The other less exact way is to use a small mallet, but be very gentle as it doesn't take much to move it.