I have a friend who had costochondritis. His would come and go, and then come back.
What you described sounds a lot like a digestive problem to me given that I have recently gone through something similar that lasted almost two full days.
I did not know I was allergic to cranberry juice until I drank some. I had severe stomach, esophageal and chest pains from that. Stupid me. Took a Tums. Did not work. Took another. Discovered cranberry juice acid and alkaline *do not mix*. I was burping foamy stuff all evening and then had severe diarrhea.
Everything went away the next morning except the chest pain. I felt like I had pulled every internal organ around my rib cage. It finally went away by the next night but it was awful. Have never had a heart attack but wondered if I was having one. If it were not for the other things (stinging swollen glands and burning tongue), I would have been calling 911.
Keep a watch on it. If it does not come back, it probably was from throwing up the popcorn. If it does, it might be costochondritis. My friend said that sometimes that would affect his ability to take a deep breath.
Let us know how it goes!