I just saw your question posted on may 19, 2012. ( june 29). though it is late, as this was posted in public forum it will be useful to others.
Fall from cot is virtually occurs in every house. several research papers have been published.
The following is the summary
1. Upto 3 feet fall : that is falling from a height less than 3 feet is ok
2. Loss of consciousness
for more than 10 minutes is dangerous.
for more than 6 times in the first 24 hours is dangerous
4. Bleedinf from the ear.
Since these where not prescribed I assume they were absent.
Your child is safe.
Other reason is : Brain damage
occurs only due to the vibrating force. Nine and a half months old means skulls will be soft, the impact will be less; Just like a soft ball landing.
Adults head is hard like a coconut, hence cracks can occur.
It will take several weeks for the bump to normalise.