Since last night, I've been having terrible ear pain. Could it be an ear infection?

It is possible that your cold has caused mucus to travel from your throat to your ears, which can lead to ear pain. To help alleviate this, you can use a product like Sinus Rinse™ to reduce the mucus in your nose and then a nasal spray like Otrivin™ or Dristan™ to open the Eustachian tube. After using the nasal spray, you can try the modified Valsalva technique by pinching your nose, closing your mouth, and blowing while swallowing to help drain any fluid in your ear. If this doesn't improve your pain after a few days or if you have a fever, it may be best to consult a doctor.