How long have you been shooting pistols? - If not long, have someone who has more experience shoot it before doing anything. If you're new to handguns, don't shoot at 25 yards, start out at 3 and work your way back, using small targets (3x5 file cards). If it actually is the gun (someone with a lot of experience has the exact same problem) the way to solve it is by gently lowering the height of the front sight with a fine file, basically it's one stroke, test - one stroke, test, - etc.
