What Causes Soreness In The Lower Abdomen After An Injury?

Hi Dr. Rynne, I had a fall on my porch 4 days ago, tripping and falling face forward. Other than quite a few bruises and generalized soreness I didn t feel I had done anything more serious than that. However, I have noticed an increasing sensation of lower abdominal soreness, almost like I have done too many sit ups, except that it has been in the lower abdominal area along the belt line. This morning as I was turning over in bed I felt a severe burning sensation to the left abdominal side. However, when I turned to the right side, I also felt it on that side but nowhere as severe. I feel it must be related to this fall. I am not sure if I need to go to the ER or just schedule an apt in the next day or two with my physician. I am wondering if I may have some sort of blunt trauma injury, and, if so, what can that cause? Thanks!