Can I play Fiery Flint if I only have 1 card in my hand to discard?
No, you must be able to discard 2 cards in order to use Fiery Flint.
Source: TPCi Rules Team (2018-09-27)

Relevant cards

Note: All applicable cards may not be listed below.
SM75_60
SM75_60a
SM75_60a
SM75_76