finish or have finished? what is the difference?

[keannu]

I already know the both can be an answer in the following, but I'd like to know the difference in detail.

A: Can I borrow your hammer for a moment?
B: No, I'm using it. You will have to wait until I (finish, have finished)

"Have finished" seems to mean an action should be finished by some point in the future, and "finish" seems to mean something similar, but I'm not sure of the latter.

[Raymott]

I already know the both can be an answer in the following, but I'd like to know the difference in detail.

A: Can I borrow your hammer for a moment?
B: No, I'm using it. You will have to wait until I (finish, have finished)

"Have finished" seems to mean an action should be finished by some point in the future, and "finish" seems to mean something similar, but I'm not sure of the latter.

"Finishing something" is an event. It takes place at a point in time.
"Having finished something" is a state which exists after the event referred to above.
So you can wait until the even occurs (I finish) or until the state exists (I've finished).