Welcome to the Bunnings Workshop community @balnda. It's fantastic to have you join us and many thanks for your question.
The end of the drip line needs to be blocked off to distribute water along its length. It appears you've installed tap valve there, so the easiest way to do this would be simply turning the tap off. It's actually a great idea that you've placed a tap in that location, as if the drip line becomes blocked, you can open it to flush the line out. You might like to add a 13mm hose clamp to make this fitting more permanent.
Please let me know if you need further assistance or have questions.