When you break a spoke it is usually not that big of a deal.   Open the brakes and keep going.   Also as I learned today don’t wait to stop as soon as you can and secure the remains of the spoke or this can happen to you:

1 shredded derailleur (thank goodness for e-bay)

1 bent dropout (thank goodness for the Bike Coop here in a couple days)

1 twisted chain (thank goodness for chain tools and a spare I can use later)

Ugh.