I chewed gum a lot yesterday and now my jaw really hurts, should i be concerned?

Maybe: You most likely over stressed your muscles with too much gum chewing. You also may have a problem with your muscles called Myofascial Dysfunction and if you aren't feeling better in a few days have it checked out by your dentist.

Muscles overwork: Muscles overwork. Those muscles are simply worn out from the constant activity. Take a break from chewing gum, soft diet and OTC NSAIDs and you'll be fine.