The Black Sea Fleet is based at Savastapol in Crimea, it controlls the sea of Azov and most of the Black Sea and is the reason grain exports from Odesa have been so difficult, I imagine it does include submarines, it does have a capability to launch cruise missiles which can be armed with nukes.
Black Sea Fleet - Wikipedia
en.wikipedia.org
7 diesel attack subs (with some land attack cruise missiles - but I don't think they are nuclear armed, some airborne attack missiles, torpedos and mines).
IIRC 2 of them are outside of the Black Sea, in the Med, and can't get back in... subject to Turkey, so they've probably gone to the Northern Fleet in Murmansk, as they'll have limited endurance, compared to Nuclear powered subs.