Hi,
I increased the width of a track and now it is violating the clearance in multiple places. I just have to drag it, but when I select an edge and drag it to fix the clearance at one place, it gets back to its initial position as soon as I release de mouse button.
I think this is because Kicad detects issues at other places on that track.
Is there a convenient way to fix clearance without rerouting the track?
Often this is the result of there just not being enough room on the PCB for the wider tracks. The way the Interactive router behaves in details like this is also continuously being tweaked and improved. Considering that, you may guess it’s useful to add your KiCad Version number, but it probably won’t matter much because such details are hard to know consciously or match to a KiCad version. 
Sometimes it also helps to bump another track or via into the offending track. The interactive router then attempts to move and re-route the offending track.
In Route -> Interactive Router Settings, which mode are you in? (If not Shove, give that a try.)
Thank you. Shove worked perfectly for my case.