Recover from a Spin in a Piper Pa28 Warrior

Firstly, the Piper Warrior is NOT CLEARED for intentional spinning. However, should an inadvertent spin occur, this is what you do.

Steps

Check the ailerons are neutral.
Close the throttle.
Apply and maintain full rudder opposite to the direction of the spin.
Push the control column fully forward.
When the rotation ceases, centralise the rudder.
Gently ease back the control column to recover from the dive.
Fly home and land immediately.
Explain to the chief flying instructor, who somehow knew what had happened, how you came to be in the spin in the first place.

Putting your PA-28 into a spin to see if you know how to successfully recover from it is a Bad Idea. PA-28's are not certified for spins. Spinning your PA-28 is a good way to remove its wings in flight.
Things which might cause spins; near miss with A380, seeing how slowly you can fly in an increasingly tight circle. This last one certainly can cause an inadvertent spin.
As well as relief and a little admiration that you, a novice pilot with only a few solo hours, managed to recover from the spin, there'll be much anger that you got into it.
Here are things which do NOT cause spins and should not be proposed as reasons; bird strike, clouds, looking at the nav chart, trying to reset the timer on your watch, singing with the joy of flight, explosive decompression.
Your silence about how it occurred will not help.