Last week I was visiting grandma in bay ridge BK and also heard/felt a huge explosion. I don't know what it's called, but the pressure in the sewer tunnel I guess overloaded (?) And the sewer cap blew off.

FDNY was also spraying down cars and sewer caps within range, assuming to prevent fires. But the smell when you stepped outside was rancid, so I'm assuming it could've been similar to what you experienced