Please need help asap

I was changing my 6 month old and she was on a couch. Well I went to go throw away her dirty diaper and when I reached the trash can I heard a loud thud. I ran into the living room and found her on her stomach crying. I have no idea what to do. I gave her a bottle to quit crying and now she's sleeping. Idk if she hit her head or what. Please help I'm freaking out.