Sperm is a symbol of creative potential and the seed of something new. Dream tradition reads it as fertility of ideas and plans as much as of the body.
Has this come up in your dreams before? What was going on in your life then?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.