I have some better pictures.

The first two are normal leaves:

And this is one of the weird leaves:

As you can see this leaf is not symmetrical. There are even worse leaves than this, they looks weird from the time they were young. (they were not normal leaves that change shape later, they were created this way).

Can someone help me please?

I can't give a reason. Quite possibly just some sort of physical damage at an early stage of growth. But it really isn't anything to worry about. If you don't like it you can just cut it out. These things need constant pinching anyway to keep them bushy. I am sure new growth will get back to normal - although variability in leaves is very common and might occur again.

It is time to conduct an experiment and root a cutting with that anomaly. If this is a sport bud, you are likely to get the same anomaly with the new cutting, though reversion may occur as well. It is also a good idea to search for abnormal growth on different and seemingly unrelated locations. This may indicate sporting induced by a virus, or insect damage. The latter being ephemeral, while the former may hold-on.