[OAC_Sparky]

Your clutch master cylinder drives a slave cylinder that moves your clutch in and out. If the oil in your master cylinder got low enough (or you have some sort of seal leak in the master cylinder) that you have air in the hydraulic line between the master cylinder and the slave then it will make the pedal spongy and the clutch will not properly disengage.

So what you mainly need to do is to bleed your clutch hydraulics line. Of course, it would make more sense to replace your clutch master cylinder at the same time because you'll need to bleed it then anyways.