How worried should I be?

My little one is 10 months old.

She caught something from her brother about 5 days ago, had a low grade a for few days, still has lots of congestion, but today she has less energy than other days.

I’m a bit concerned because yesterday, unrelated to the cold, she was playing in her padded play pen, sitting on my lap, when she bent forward and smashed her head into the thin sharp edge of a plastic stacking cup—had a bump on or near her temple, screamed for a minute or so, but then calmed down. She had a small bump, which has already disappeared. When I tried to get her to nap shortly after she fell, she screamed and wanted to be held, and was unusually inconsolable. Now, she was also congested overtired, but she normally falls right asleep when she’s this tired. I picked her up and brought her downstairs and she calmed down and smiled. When I tried again later, she cried for a while but then fell asleep. She was happy but calm when she woke up about an hour later. Last night she was a pretty normal, played in the bath, etc.

But she slept unusually deeply at night - 12 hours straight. And this morning she’s quite groggy. She played with stacking blocks and walked around in her walker, but didn’t scream with enthusiasm as she usually does. And now she’s ready for a nap on the earlier side.

So, my question is: should I be concerned about a brain injury? It seems silly because the fall wasn’t from a great height, but it was onto a hard plastic edge on the temple. Or could her lethargy be caused by her cold even though we are on day 5 of the cold and she had more energy on previous days and currently has no fever?

Thank you for reading this. I am so worried and I feel like the worst human being on earth. We have an appointment today to get her evaluated, but I am a nervous wreck. I just want my baby to be healthy and happy. I can’t believe what I did: she was cuddling with me in my lap and I let her just fall and hit her head. How could I?