I feel tightening of my temples after i chew on something hard like beef jerky. what is the cause of this?

Temporalis muscles: You are stressing the jaw chewing muscles on the sides of the head - temporalis muscles. No problem, should resolve. If persistent, cut back on the jerky.

Muscle Strain: This is a pretty common problem. It happens to me on occasion. Beef jerky is hard to bite through and causes your muscles to work that much harder. Try cutting it in pieces so you jaw doesn't have to work so hard! Hope this helps!