1.7.10 launcher won't let me Play Minecraft?

My cousin logged in on my computer without my permission and him being a Minecraft addict Went straight to Minecraft. Long story short he logged in to his account and when he exited out it says "Loading…" And "Welcome, Guest! Please Log In.Ready to play Minecraft 1.7.10" Under that it says "Switch User"
It has been like this for ten minutes and when I click "Switch User" nothing happens.It just does nothing. What did he do? I know you might be like it says "Please Log In Just Log in Like it says"
But It literally has nowhere to log in.So Yeah Please Answer.
Bye!