The readings are the kun'yomi readings. With 側 you've already learned it. With 内 you've also already learned the reading. Combine them together and you have うちがわ. In case you've forgotten, here's a mnemonic to help you remember that pesky うち portion. What is it that's drawn you inside? "Oo, cheese!" (うち) Cheese has drawn you inside. You're so excited that you exclaim, "Oo, cheese!"
I'll wait for you inside Resona Bank.
I think I've got a splinter in my inner right heel.
We need to lower the metal shutters and lock them from the inside to shut the zombies out.