Will I get bad ear pain on an airplane if I have a small cold like only a stuffy nose? If yes, will chewing or yawning prevent it for sure?

Valsalva. Chewing or yawning will help release the pressure. A valsalva maneuver where you hold your nose (pinch it) and blow gently will equalize the pressure when needed.
Answers: Maybe, No. Any kind of sinus congestion could block the eustacian tubes, causing mild barotrauma (ear pain) to the tympanic membranes. If you have a cold and absolutely must fly, a good trick would be to use some over the counter Afrin (oxymetazoline) just before boarding the plane. This should prevent any problems. Be sure to throw it away after boarding though because any more use will put you at risk for problems.