Injured turtle shell/struck by car

Please advise me about care for an (box?) turtle that I just found. He had been struck by a car, and has a "tear"; about 2 inches wide, between his right front leg,and his head,

I am sure that you will say that I need to take him to a vet? Unfortunately, this is not an option.
I appreciate your time and look forward to hearing from you.
Thank you.
Tammi Coffield
#(405)321-5932
(please feel free to call collect)
tjz0o@yahoo.com