Only INPUT pins on net PIN5
This error is caused by pin 14 of IC6 being labelled as an INPUT pin. The ERC has noticed that there is no corresponding OUTPUT pin connected to the PIN5 net, so it believes there is an error. Since you are building an arduino shield, you can safely ignore this error.
Only one pin on net PIN5
Eagle is saying that it sees a net, called PIN5, that has only one thing connected to it. This error should not be ignored. Without seeing the rest of the schematic, it's hard to tell what the cause of this error is. But I'd guess that you have not added the shield's mating connectors (or have not labelled the connector's pins). Once you add the mating connector to the schematic and connect the corresponding pin to the PIN5 net, that error will go away.