Yes, rot. Peel off the leaf with the brown spot, leave the plant in a dry spot for a day or two, then repot and be careful with watering. The other roots probably rotted off also. When you repot, be sure to make it a fast-draining soil by including plenty of mineral matter - I use crushed granite.

Thank you for your answer :)
My mix has more than 50% (like 70%) of perlite, is that not enough ?
And I'm pretty sure I'm not overwatering it, if anything I'm probably not giving it enough water.
And also I'm afraid if I cut the leaf with the spot I'll loose the roots :( because the leaves go around the plant). What will happen if I leave it ?? Will it spread??

With that much perlite, your aloe should not be able to stand upright! Ij any case, if you do not remove the rot, it will spread and kill the plant.

Some aloes need remarkably little water, especially in colder weather.

It does stand though ! I put small rocks on top of the soil and it works just fine.
If I don't have a choice I'll cut the leaf, but the roots took one entire month to appear :( and I don't want all my work to go to waste.

Is this a just-rooted cutting? If so I don't think that brown patch is rot, just the callused cut.

Yes !! I cut it from the mother plant a month ago and I saw the roots about 2 weeks ago :)

If the brown spot is squishy, treat it as rot. If it is solid, I would just repot it an keep an eye on it. It' only been a few weeks since this things rooted, I wouldn't expect it to have more roots than that...

Ok I'll do that thank you so much !!!
But the problem is that there are roots on one side, and the side with no roots is the one zits the brown thing. I will see if it's squishy or not tonight when I go home :)

Don't worry about the roots not being equally distributed, more will grow I time..

It didn't feel squishy at all when I touched it. Here is a close up of the thing, maybe it can help you identify the problem :)

Went to check on the plant noticed that the leave that was turning brown was yellow on the tip... So I decided to just take it down, no roots have been lost. Just wanted to let you guys know :)