Is cortisone injection absolutely necessary with thick-skin/oily nose if swelling is still there one year post surgery?

One year post rhinoplasty and I still have swelling on my nose tip. I got thick-skin and oily nose. Today my doctor did an cortisone injection for me and wants to see me again in 3 months from now. QUESTION: Is the goal of this injection to "accelerate" the going down of swelling? or the swelling, or part of it, won't go away without the injection? In other words, if I let it recover naturally, will I have the same result as injecting steroids? Thank you.