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You may need to let it cool down but if that fails to fix it then I'm sorry to hear this but you would need to either return your device to the place of purchase or contact Xperia care and have your device inspected http://www.sonymobile.com/global-en/support/contact-us/
What device do you have?
Hi insu, welcome to the community!
Follow @Thommo's advice and let it cool down a bit and try restarting it, if it still doesnt restart you could try doing a software repair on the handset to see if that helps - otherwise contact Sony Xperia Customer Care in your region, just click the link in my signature for details.