i assume you mean you have rounded the hex head on the bolt?

if you have you may get it like you've said, by hammering on a socket (make sure its a 6 point though )

or you could drill through the head with a drill the same/slightly larger diameter than the threaded section of the bolt, this will remove the head and leave the threaded section of the bolt in the head. Then all you'd have to do would be lift of the cam cap and unscrew the threaded section of bolt.