Basically I wanted to open my MacBook Air and when I started writing in my password all letters were in all caps. Therefor, I plugged in my keyboard and it worked on the email Registration but not on my password. I am wondering if someone might have hacked my password and if so what I could technically do to stop him. This is a very urgent problem as I need this laptop for my school work, thank you for anyone answering.
2-3 hours before this happened a small ball fell onto my keyboard
What you have described are not the symptoms of a hack. It sounds like something is broken on your keyboard, and something was dropped something on it. You will need to get the keyboard physically repaired.
I am wondering if someone might have hacked my password.
No.
'Strange behaviour' is not usually the symptom of hacking or malware. Such activity wants to go unnoticed. Malware wants to sit on your computer quietly, without attracting attention, harvesting your keystrokes or other data.
Hackers also are unlikely to change your password, but to keep using it quietly. (And likely we're talking about automated processes that are using stolen databases of passwords and usernames - no individual is singling you out, unless you're of interest to a nation state or commercial espionage.)
Given the fact that you mention damage to your keyboard, and then problems using it, then that's the much more likely cause.
