I'm 8weeks 2days pregnant and have a 1cm subchorionic hemorrhage. what you suggest to ensure the hemorrhage doesn't get any bigger? bed rest?

Nothing: You don't need to do anything special. Enjoy your pregnancy. The vast majority of small subchorionic hemorrhages resolve spontaneously. Use common sense and avoid dangerous activity or unusual exertion. Otherwise, alert your doctor for cramping, pain, or bleeding.

Pregnancy bleeding: A subchorionic hemorrhage/hematoma is an US finding, that if coupled with vaginal bleeding, can potentially increase the risk of miscarriage/preterm delivery, but w/out vaginal bleeding, it's hard to say. Size matters; worse if bigger (covering ~50% of placental bed) or occurring later. It can heal itself, but you just have to wait/watch. Bed rest/medications don't help.