resistance measurement problem with digital multimeter
It sounds like you blew out the meter.  Get a new one, and this time don't do something stupid like plugging it into the AC line on the wrong scale.

This time get a meter with a proper fuse.  Good meters will simply blow a fuse when you connect the leads to the AC line on the current scale.  Still, no matter how good the meter, it can't protect against all manner of cockpit errors.  At some point you have to take reponsibility, which is where you are with your old meter.

You messed up.  Learn from it and move on.