As a matter of utmost urgency, which ever pad came away from the plate, you need to change this imminently.
The pulsing/judder is probably a warped disc.
You'll not see this with the naked eye, but it's enough to cause judder, it may even be only one disc.
In my experience the front ones seem to be the first culprit.
Id suggest changing the pads asap, give them a day or two to bed in.
If this doesn't resolve the judder, start by changing the front discs.
Provided you do this within days of the new pads, you get way with using the same pads.