Today Since morning for the first time, I'm hearing a grating/cracking sound whenever I chew on my left side. Will this go away if I rest my jaw?

Rest, ice. Sounds like you have developed a problem in the temporomandibular joint. Try resting it as much as possible, ice and some anti-inflammatory medicatons like motrin or aleve (naproxen). If this does not relieve the symptoms in a few days to a week see your doctor or dentist.