Can I receive Bumps even after the workout is over?

Yes, as long as you don't discard the workout, Bumps can be received at any time.  Go to your Recent Activity often to check if you have any New Bumps on the Workout History card.  All New Bumps will be highlighted (see pic 1 below).  Tap on "Bumps" to go to the Bump screen to play them (see pic 2 below).

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