If a piece of it is protruding and you have some stout tweezers or fine needle nose pliers you can grip it and pull it straight out. If no part is protruding and you have a really steady hand you can glue a plastic toothpick to it with superglue or gorilla glue, let it dry and then pull out the toothpick (straight out).
One other method I've use successfully a few times if the broken part is not protruding far enough to clamp, gut is protruding a bit past the body of the iPhone or slightly in cut a strip of duct tape, use something (butter knife will do) to push the sticky side onto the broken piece then pull off the tape straight back.
If you don't want to try any of these see if a 3rd part repair shop is open in your area or click on the Contact Support link at the top right of this page to arrange to send it in for service.
DO NOT try the glue method unless, as I said, you have a very steady hand and can place the glue ONLY on the broken piece and not elsewhere in your iPhone. You could cause damage. The other suggestions, including the duct tape, will not damage your phone.