Russia has air, sea, and ground launched missiles that could target shipping. They could do so even if they didn't occupy Crimea, and this strike probably doesn't really change anything in that regard.
But the farther Ukraine can push Russia away from their coasts, it becomes more difficult and expensive to maintain a blockade. FWIW Ukraine has already had ships defy the blockade, and they have not been targeted. Hard to see any way for Ukraine to unilaterally deprive Russia of the ability to credibly threaten Black Sea shipping though. Until there is some sort of diplomatic agreement regarding shipping, there will be a risk that Russia may target it.
But the farther Ukraine can push Russia away from their coasts, it becomes more difficult and expensive to maintain a blockade. FWIW Ukraine has already had ships defy the blockade, and they have not been targeted. Hard to see any way for Ukraine to unilaterally deprive Russia of the ability to credibly threaten Black Sea shipping though. Until there is some sort of diplomatic agreement regarding shipping, there will be a risk that Russia may target it.