What Could Be Causing Worsening Pain In My Lower Right Rib After Feeling A Pop During An Incline Leg Press?

Good morning. I was at the gym last Wednesday and on an incline leg press. When I pulled my knees to my chest and started to push I felt a pop on my lower rib on my right side. There was slight pain in the area, but I was able to finish my workout. I went back to the gym Thursday, Friday and Saturday without too much pain. It is Monday and the pain is the worst it has been, but I am able to handle it with Ibuprofen. Any thought or ideas on what it is?