How to check what is the last object collsiion?

If I want to check the last object that collided player is the same object before.

How can I do?

I do not know for what purpose will be used, then it will be hard to tell you something that is fully tapped.

I might put a boolean type variable in the objects I want to identify the collision and after the player colliding with these objects would change their variable from false to true.

this will always give you a way to know who already collided with the player or not

If you want to know if it is the same object as the last collision (as opposed to just if it has collided before) On collision store the name or UID of the object in a variable, then on the next collision check the variable and see if it matches.