Why won't my touch screen work?

Why won't my touch screen work?

I was waiting for a text from a friend. I put the phone on my lap and waited for it to say 1 new message. I tried to hold the unlock button, but it wouldn't work. So, I turned off the phone and turned it back on. Still no response. Is there any way I can make the screen work? Do I need to bring it in the phone shop? Any suggestions?