until today and possibly still in the near future both bitcoin and bitcoin cash are using the same keys. this means private key of bitcoin is the same as private key of bitcoin cash.
if you have a bitcoin cash address and send bitcoin to that address you can simply export that private key from your bitcoin cash wallet and import it in bitcoin wallet and have your funds.
if that address belongs to a service like an exchange you need to ask them to do it for you but they may not.

in the future bitcoin cash may change the keys to have a new address format in that case you will be unable to send anything to those addresses because if you put that in your bitcoin wallet it will reject it.

p.s. be careful when using bitcoin cash wallets they may not be as trusted as you may think.