How to get original php code for my wordpress theme?

I am totally new to this stuff and I made a bad move. I tried modifying the php code in my WordPress theme and now it doesn’t work. And I can’t get back to the original code. Help! How do I get it back? It is the Boldy theme. I don’t want to reinstall because I will lose the good changes that I made. I just want a copy of the original code so I can see what I did wrong.