Delete block settings when removing a block from hook_block_info()
I hope this should work if I get your question right.

db_delete('block')
  -&gt;condition('module', MODULE)
  -&gt;condition('delta', DELTA)
  -&gt;execute();
db_delete('block_node_type')
  -&gt;condition('module', MODULE)
  -&gt;condition('delta', DELTA)
  -&gt;execute();
db_delete('block_role')
  -&gt;condition('module', MODULE)
  -&gt;condition('delta', DELTA)
  -&gt;execute();

cache_clear_all(MODULE_DELTA, 'cache_block');


Where MODULE resembles your module name and DELTA resembles your block's delta.