can anybody help me please?

Can anybody help me please by answering my question. I had my phone taken away by my mum.... because Its a punishment. But because I'm stupid I decided to go onto the find my iPhone app and accidently clicked on the 'Lost mode' button. But because I turned my iPhone off, Lost mode will not activate till its turned back on again. What will happen when I get my iPhone back and turn it on? will it erase everything? and how do I turn it off in the mean time? Thank you, any help will be greatly appreciated.