They are male flowers. If there are only a few, you can try pulling them off with tweezers, but if they are everywhere, removing the plant affected out of your grow area may be your only option, if you don't want any seeds everywhere. If you are keen on a bit of experimenting, you could leave them and hope to use the pollen on another plant to hopefully breed some hopefully female seeds. (that is a lot of hoping though!) Self pollination could lead to inbred and hermaphroditic offspring.