The inductor develops magnetic field around it to store the kinetic energy of the electrons into magnetic field, but i don't have a clue why does it opposes the change of current passing through it and how .. i know the Lenz's law but don't know the physics behind that..
The opposition to change in current is observed because the inductor is extracting power from the current and storing it as energy in the magnetic field.
So, if the current is increasing, the magnetic field will build up (which takes energy). This energy must come from the current and is extracted by causing a positive voltage across the inductor.
If I wanted to store some mechanical energy I could push a rock to the top of a hill. Easy to do? No, because the rock fights all the way until I stop pushing.
If you want to take energy out of one system and put it somewhere else, of course there's "opposition". You don't get energy for free.
Natural systems tend to not like change, they want to keep equilibrium. An inductor is a classic example of a natural phenomenon which is this way. An inductor wants to keep the current steady so when the current changes it fights to slow the change by developing a voltage in opposition to the amount of change. If you want to fully understand electro-magnetics, study Maxwell's Equations which are the set of 4 equations that describe most of what you need to know.
The opposition to change in current is because the magnetic field built up is at a right angle to the current. This magnetic field, being at a right angle, imposes a current in the windings that tries to make the current flow at a right angle in the core (ferrite or silicon steel), instead of a smooth flow. This is sometimes called an 'eddy' current. It creates a resistance to the current your want to drive the inductor or transformer with.
It is at a right angle to the normal current flow and can lower the effectiveness of a transformer or inductor a lot. To compensate for this most all power transformers made of silicon steel are done in thin layers lacquered together. The coating keeps current from flowing at right angles while allowing the magnetic field to work normally.
Ferrite cores for switching power supplies spread the windings evenly as possible around the core if it is a toroid. If it is an 'E' core type a small .010" gap can be inserted between the 2 'E' shaped halves to lower eddy currents and prevent core saturation at high power levels.
Whether it is an inductor or a transformer the same rules apply because they are both subject to the same problems.