Opened the door into my stomach today

I accidentally opened the car door right into the side of my stomach today. Like right into it. It hurt a little bit, but the pain went away very shortly after. A little later I had some very slight cramping for a couple minutes. I checked the heartbeat a couple hours later and it was fine. Ive felt baby kicking throughout the rest of the day.  I'm 21 weeks. Should I be worried?