I don't know how to phrase my question better, but I just want to know if there will be any little difference if I directly replace one with the other.
I think we can generally divide them like this, although the separation may not always be so clear.
To study is the action, (from the dictionary) "the devotion of time and attention to acquiring knowledge on an academic subject", so the activity itself.
To learn is the result of that action, or as you can see in the Dictionary again, "gain or acquire knowledge of or skill in (something) by study, experience, or being taught".
Well, you can study without learning, but you can't often learn without studying, at least in academic subjects.
Saying "I studied English" means you took classes in English. It does not necessarily mean you learned anything. Saying "I learned how to tie a clove hitch" means you actually acquired a useful skill.
To learn is a much broader term than to study. I agree that learning is a result, but it is most often a result of no conscious action on our part. We learn from the moment we exist, taking in the lore (related word) of language and customs of those around us through all of our senses. We learn every moment of our lives, even while sleeping. When we study (from Latin studium ‘zeal, painstaking application’) we make a conscious effort to learn a specific lore. Learning is always the result, even if what we learn is that we can't make heads nor tails of what we are studying. But learning is a given whether we study or not.
I consider the difference more than subtle.
You can study without learning and, yes, you can learn without studying.
Studying is the act of trying to gain information. It generally results in learning. Learning is acquiring new information. It can result from study, but also from everyday life and experiences.
They are very distinct - study implies some kind of focus, while learning can happen by perhaps a broader mechanism. Usage would depend upon context. Study also can be a verb or a noun, so that might influence using or avoiding it depending upon context.
FWIW, the term "study" is not used, for example, when discussing work towards degrees in England (at Oxford or Cambridge) - in that case the term used is "read", as in "I read Maths at Cambridge", or "What is Sally reading at Oxford?"