After Oracle 11gR2 restore & recover database, "ghost" NOLOGGING corrupt blocks
Presumably there was data in them at one point, which has since been deleted.
If the corrupted blocks are in free space, there is no need to take any action. Oracle will reformat the block when it attempts to use the space. So you can ignore the alerts.
If you want to clear the corrupt blocks to prevent more alerts, create a nologging table in the relevant tablespace. Insert a lot of rows until the corrupt blocks disappear, then drop the table.