HTC — Htc 816g dual sim. complaint about-cannot access my camera.

Iam having HTC 816g dual sim. When I get into camera. I get a pop up window saying "CAN'T CONNECT TO CAMERA". I can't understand whether it is a software or hardware problem. I didn't put my phone down or hit it. It just happened when iam normally using it. So I should get a proper reason for this and this problem should be solved and given for me. Thanking u.