What is the best solution to get rid of a medium indention mark on nose...Is plastic surgery the best or only option?

Not necessarily. Small irregularities on the nose (and face) can often be treated most effectively and efficiently with injection of a filler such as Restylane (dermal fillers) or juvederm. Though these are temporary, they will tend to last for 6-12 months in the nose, can be injected in the office with local anesthesia, and do not require an operating room. Surgery can always be an option, but i would try the fillers first.
Nose dent. A filler or fat graft may work unless it is due to underlying cartilage issue, then surgery may be required.
Nose scar. An indentation mark on your nose may be caused by various issues. It should be evaluated by a plastic or facial plastic surgeon. If due to a problem with the underlying bone or cartilage, plastic surgery may be appropriate. If due to scarring in the skin, laser resurfacing or a scar revision may be of benefit. Another option is for an experienced physician to use injectable filler materials.
Difficult to say. The best solution is to consult a plastic surgeon or ENT doc in person. Without seeing what is causing the indentation it is difficult to advise.