might be a stupid question

[kenny1999]

is this dirty stain on the plug a problem? unable to clean it up

from newly bought ipad mini, bought from official Apple store.

 

[Aspasia]

Does the plug work? If so, not a big deal. If it bothers you, take it back to the Apple store and request a replacement.

 

[Rodster]

Take it back and they'll replace it. There was a story posted and it could have been on MR that shows the new lightning cables and connectors for some reason suffer from corrosion. The article also indicated that Apple is replacing them free of charge.

You could also call Apple support and they will probably send you a new one.