on the spot
US /ɑn ðə spɑt/
UK /ɑn ðə spɑt/

1.
immediately; at once
:
•
He had to make a decision on the spot.
•
The police arrested the thief on the spot.
2.
in a difficult situation from which it is hard to escape
:
•
His boss put him on the spot by asking about the missing funds.
•
I was put on the spot when asked to sing at the party.