It's like saying youre scared to workout because you'll get "too bulky". bones adapt to force, you may even see some mandible growth if youre still in puberty.
It's really hard to have too wide of a jaw, I wouldn't recommend more than like 20 mins of chewing rough foods a day. Anything over that is overkill.
Stop and see a doctor if you hear clicking or experience pain.
Goodluck!
edit: chewing tough meats, dried chickpeas, carrots and apples >>> mastic gum because you get calories and it's obviously more natural