Can raw soured milk be used to make cheese
Actually, you might.
 Depending on the strain(s) of bacteria in your milk, you might be well on the first steps for making "Handkäs", a speciality from the Frankfurt area in Germany. It uses no curdling agent like lemon juce (for fromage blanc) or rennet.

Try this recipe, (english version at the bottom):
Handcheese with music