Keep the Crown. Call the Dentist.
Save a detached crown safely, describe what happened, and arrange dental advice before trying to put it back on the tooth.

Save the piece safely
If a crown comes off, keep it in a clean container and contact your dentist. Do not use household glue or force it back into place. A loose crown in your mouth can be swallowed or inhaled, so ask for specific advice before attempting any temporary replacement.[1]
Describe whether there is pain, bleeding, swelling or a broken piece of tooth attached. Tell the office whether it is a temporary or final crown if you know. Keep chewing away from the exposed area while you arrange advice.
Ask what has to be checked
The dentist needs to assess the crown and underlying tooth before deciding whether it can be reused. Bring the saved crown to the visit. Ask what the examination will establish and whether any provisional protection is needed.
When booking, explain symptoms rather than asking for a simple recementing appointment as though the answer is already known. If symptoms worsen while you wait, call again. Ask about the fee for assessment and the likely next steps, leaving room for the findings to determine the repair.