[lxndr]

Bleed the brakes.

The wheel cylinder (brake cylinder) should not be effected if you accidentally pull off the rubber dust cap, unless you manage pull the cylinder completely apart. If this happens you will need to re-assemble the wheel cylinder and bleed it. It is normal for there to be a couple of drops of fluid behind the dust cap, but if there is more than a couple of drops then the wheel cylinder seals have gone bad and the cylinder should be rebuilt or replaced.