I belive that you don't have much choice on this one.

Best option imo is to leave it alone.
You can trim the cel if you wish to get rid of that torn 
depending on how big it is.
 
or you can tape it with clear tape...or i wouldn't 
recommand but you can try to light the torn part of cel 
and melt the top part for them to come into one 
piece..o_O   

gl ~