Is it safe to wear contact lenses when you have a subconjunctival hemorrhage?

It can be: As long as there is no discomfort wearing them, it can be safe to use contacts even with a subconjunctival hemorrhage. A few words of caution: if the bleeding was caused by a scratch or foreign object, or if there is a significant amount of swelling from the bleed, you should not use contact lenses. Prior to using the lens, you may want to have your eye checked by a doctor.

Sometimes: I would caution against wearing a contact lens if you ar having any scratchy sensation or discomfort from the conjuctival hemorrhage.

Yes: There is no problem with doing this.