Hi Kass
It is a lot harder to pick a concussion in a small child/baby than an adult or an older child.
Things too look out for are
* is she behaving normally?
* can she do the things that she normally would
* if previously she would grab for a certian object when you held it to her, see if she can do that.
* is she more sleepy than usual?

If she is acting differently go and get her checked out and tell the hospital that she is acting differently. If she is not she will be fine.

It is amazing how hard you can hit your head without sustaining a concussion or injur other than an egg on your head.
I would watch for 4 hours - if there has been no change in this time she should be fine... that is how long she would be watched for at a hospital if they were concerned with her.

Try not to worry if she is acting normally thou - we have very hard heads!