I bumped into a car with my bike today and the guy saw me do it.
Did you mean to hit the car?
It wasn't my intention to do it. My bike is pretty old and difficult to steer.
It's not safe to ride a bike that can't be reliably steered, so you should get that fixed.  Furthermore, you should take responsibility for any accidents that you cause on the road, because they can be costly, and you are legally required to make amends.
I am going to gladly pay for the damage I caused.
I'm glad you're willing to pay for his car repairs, but you should also invest in a new bike so this doesn't happen again. You're putting your safety at risk by riding this old bike.