If your diagnosis is otitis media (OM - middle ear infection), code 382.9.
380.10 is for otitis externa (OE - swimmer's ear) involving the ear canal.
OM and OE may be present at the same time if there is a hole (or ear tube) in the eardrum; fluid can drain from a middle ear infection into the ear canal, causing swimmer's ear. So, it could be possible to see both OM and OE documented of the same ear.