After the septoplasty or rhinoplasty, for about 2 weeks or so you will experience nasal congestion, blood stained mucus during the recovery period. This will lead to temporary loss of your sense of smell due to the nasal obstruction.
Thereafter, the risk of loss of the sense of smell after the surgery (that lasts <6 mths) is uncommon, and has been reported to occur in <1% of patients.