My doctor diagnosed me with blood in eyeball. Just checking - what's the best treatment.?

Good start. You have seen your doctor and that is the best start. Bleeding inside the eye, usually associated with trauma, can lead to elevation of eye pressure (glaucoma), blood staining of the eye and visual damage especially if the retina is disturbed. Your ophthalmologist can sort this out and start whatever eyedrops are best for recovery.
Time. I am assuming it is either a hyphema or conjuctival hemorrhage. The latter is more common and I am assuming that is what you have. If you have a hyphema you should see an ophthamologist, but the it should reslove on its own. Neither require any specific treatment other than avoiding the activity that led to it.