Name changing (in files)

I had learned from a video that you could change your name by editing the Launcher_profiles.json files. I went ahead and tried this becuase the begining s in my name (skulldude2004) is lowercase and bothered me a little. And after doing so I couldn't change my skin no matter what I tried and I couldn't join any of the servers I could before. So I was wondering if there was any way to fix it.