I've Had Sharp Chest Pains Under My Left Breast Bone

I've had sharp chest pains under my left breast bone since 9pm last night. It tapered off around 3 am and came back around 11 am this morning and has been ongoing since. It started last night when I blew my nose quite hard and I felt a severe sharp pain in my left chest. The pain gets debilitating at times and I attributed it to possible indigestion, as I did eat some junk food last night that I don't typically eat. I took an antacid around 2:45 pm, which helped a bit, but now I'm still unable to take a deep breath because of the sharp pain. A dull ache also started in the top of my left shoulder as of 1pm today. Of course, worse things were in the back of my mind as to what it could be but hoping it's not serious. Could it be a pulled muscle or sever indigestion?