Hello from JustAnswer.
Could you attach a picture of the dark patch?
What, if any, chronic medical problems do you have?
What, if any, chronic medicines are you taking?
I had asked for a picture of the dark patch and have not head back.
In most cases, a dark patch 10 days after a fall is not worrisome, particularly if it is not associated with any symptoms and is gradually getting better.
Monitoring the patch for a few days to see if it is gradually getting better would be OK and as long as it continues to be gradually getting better, no specific care is needed.
If it is getting worse, that would be more worrisome, and it would be better for you to be seen.