Can Single Particles have Entropy?

I have studied online that entropy is only a property of a group of particles and never a single particle.

Thinking about this I came accross a thought experiment where I have a particle enclosed in a small box with a hole connecting to a very large box. If the larger box is infinitely large as compared to the smaller one, then if we leave this system for a while we will observe particle always ends up in the larger chamber.

So is it correct to describe this process as increasing the entropy of the system/the particle?

If yes, then here we were able to describe entropy of a single particle which contradicts the above.