What could cause soft protrusions in my nasal cavity post- septoplasty surgery?

Swelling: Most likely what you are noticing is swelling of the operated on tissues or the suture material if the surgery was recent. Most likely there is nothing to worry about but be safe and check with your surgeon.

Normal or abnormal: There re normal and abnormal reasons for this such as typical swelling or a septal hematoma. Your surgeon will be the best reference for this question.