Leather does not stain itself, it must have been done by something else. If you have a soft absorbent leather (one that absorbs moisture readily) then anything that has stained will be in the leather ans you cannot clean it out. You can only clean of...
Just sponge off with a damp rag.Don't put anything except water on rag.It may work. Otherwise there is a dry powder cleaner for leather. Failing that, check with a Saddlers to see if they sell a leather soap you could use.
If you can't touch it it is difficult, maybe you can try to check if it has pores. Fake leather doesn't have pores, it is synthetic, real leather has pores (it is skin after all), and you can see these tiny black specks. I would not risk it. Even if ...