Hi it's 3 weeks since my wisdom tooth extraction. I had earache in my left ear which I did expect but that's gone. Now I can't hear in right ear..

See your dentist. It sounds like you may have an infection and i would recommend that you go back to the dentist that removed your wisdom teeth.
See your doctor. You need someone to look in your ear today. Although it might be wax or fluid it could also be a viral hearing loss. Your primary care doctor should be able to see wax or fluid, if not you need to see an ENT doctor.
Hmmmmm. If i were you, i would first see my physician or an ENT specialist. Your problem may or may not be related to the removal of your wisdom tooth. If your md cannot find any medical cause, i would see your dentist, which wouldn't be bad idea anyway just to be sure everything is healing well.