“May I come in?” is used for asking permission to enter a room. Usually we knock and then say these words. We use the words come in as most of us walk into the room.
“May I get in?”, “get in” is used when we ask somebody whether we can jump into a boat, or a swimming pool, or get into a bus, or into a cab. This is usually not used for getting permission to enter a room, both formally and informally.
Only rarely when somebody is getting dressed we can ask informally “have you finished dressing, shall I get in now ?”
“May I get in?”, “get in” is used when we ask somebody whether we can jump into a boat, or a swimming pool, or get into a bus, or into a cab. This is usually not used for getting permission to enter a room, both formally and informally.
Only rarely when somebody is getting dressed we can ask informally “have you finished dressing, shall I get in now ?”