The problem can be because of excessive pressure exerted during forceful blowing. The hearing loss
can be because of sudden blockade of your Eustachian tube or can also be because of transient damage to your inner ear
. The blackout
part is also because of excessive pressure taking its toll. Please take nasal decongestant drops and oral decongestants for 4-5 days. If fever
is there, do take a course of antibiotics. In future also avoid forceful blowing. Regards.