Are you having blurred vision or any vision changes?
Any nausea or vomiting?
Did you lose consciousness when you fell?
Typically head injuries that are worrisome will have vomiting as well.
However, given your age and other symptoms it would be better for you to be seen for an examination. Sometimes slow internal bleeds in the brain takes up to 3 weeks to show up!
You probably won't need to go to the ER tonight unless you worsen or start vomiting but do call your physician tomorrow for an exam.