M.B.
2 of my 3 daughters injured themselves in the genital area... one was running through a snowy, slushy yard, and slipped.... and landed on a branch with a stub pointing up... she was bleeding, and screaming! We called our doctor (small town... he just met us at the back of the clinic and examined her). He cleaned it up, and just said to watch it.
The other one slipped on a jungle gym and essentially "racked" herself.... no real bleeding, but some bruising...
With both girls, it hurt to pee for a few days... the one that was bleeding moreso... with the second one, I had her use a squirt bottle (like a peri-bottle after you give birth) to squirt on her genitals while she was urinating... that diluted the urine, and washed it away quickly so it didn't burn so much. (I wish I had thought about a squirt bottle for the first one.... that would have made it much easier for her.) I don't remember how old they were, but they were grade school age at that point.
Most likely, there is some bruising, but not much other damage. If she can urinate, that will help... have her use a squirt bottle (or you help her with that) so it is easier to pee, and she doesn't try to withhold it for fear of hurting. A cold compress might help her be more comfortable, also.
If it is still bothering her in the morning, I'd call the doctor. Not seeing it ourselves, though, it is hard to tell if that warrants an ER visit.