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The first thing to do, is to not drain it again, unless drainage is done via a surgical procedure that involves removing a section of skin from the underside of the ear flap. Your veterinarian may recommend such a procedure.
If you do not wish to pursue surgical intervention, then leaving the ear alone is the best option. The fluid and blood will eventually be reabsorbed, and though the flap of the ear may curl or wrinkle, it's only a cosmetic issue and does not affect function or comfort. The only issue may be that if there's an infection in the ear canal (odor, discharge / debris, scratching/itching), then this infection must be treated in order for the dog to be comfortable.