Should I have a steroid injection on this bump on my nose? This is from a pimple that never flattened from years ago (Photo)

Your picture seems to show skin-toned bumps.  I do not see significant inflammation or redness/swelling, nor does it appear to be a thickened scar of some sort.  Though if I saw you in person, I would use a dermoscope (magnifying) light to examine for scar.  If there is no inflammation or scar, steroid injection treatment is unlikely to benefit or improve the bumps.  Instead if they're persistent skin-toned bumps, they are more likely to be benign nevi or papules (sebaceous hyperplasia, milia, angiofibroma, etc.), present in same place as a prior pimple by concidence.   It is common to get benign bumps on the nose with age.They could be removed with a gentle shave excision method by a dermatologist.  I recommend you see a board-certified dermatologist for further in-person evaluation. 

You need to be evaluated in person and it depends on what is underneath; cartilage, scar tissue etc. I recommend you have it checked out and dealt with by your plastic surgeon.