Ladies on these forums have sometimes written in about subchorionic hematomas, and though it's scary for them at the time, I don't remember one that had a problem with her pregnancy because of it. The doc will check it at your appointments, and it may just hang there or eventually actually go away. As mommy27 said, I'm sure everything is fine. If you want, you could go to the Maternal and Child Health forum and do an archive search for subchorionic hematoma, and some of those posts should come up.
I'm sure everything is fine. Think positive thoughts! When us your baby due?