I am not a doctor, but my guess is there might be some some bone-conduction hearing happening when you press the phone hard against your skull ..... which means the sounds from the phone may be transferring to your good hearing nerve through your skull bone.
If you cannot hear anything from that ear without pushing it hard up against the bone, that nerve may still not be functioning well. If, on the other hand, you can hear faintly when plugging your good ear, you might want to check with a good audiologist about a hearing aid for that ear. Only an audiogram will really give you the true answer, I think.
My audiologist explained that it is the brain that does the hearing ..... the ears are only the vehicles to get the sounds to the brain, via the auditory nerves. You may need to "wake up" the side of your brain that thought it was deaf. What I did not know before was the right ear sends sounds to the left brain hemisphere (where language is processed) and the left ear sends sound to the right hemisphere and then back to the left for language processing.
I do not live in Kentucky, but I have an excellent audiologist at the University of Kentucky (for my Ponto processor), who is wonderful in figuring out what each of her patient's hearing needs are. Hopefully, you have just such an audiologist near you.
Clarice