Should I have a nose surgery? My friends made fun of me for years. Now im 18 and ready to go off to college.

Yes. If this gets frequent comments, it will prove to be a personal and professional liability as an adult. It's wrong, but it's a fact of life.
Evaluation. I will be your decision and you will need an evaluation from a Facial Plastic Surgeon or Plastic Surgeon. Hope this helps.
If you want to. If your nose bothers you cosmetically then prior to leaving for college is an excellent time to consider rhinoplasty. But, only do it if you want to, not because your friends tease you. You should only pursue cosmetic surgery because you have thought about it, and are motivated to improve a feature because you want to.
Possibly. If you are happy with your appearance, then don't worry about high school ridicule. However, you may want to see a facial plastic surgeon who specializes in aesthetic surgery of the younger patient, not the aging patient. S/he will do a complete facial analysis, which is very mathematical, and then advise you on whether your face is proportioned, or if it needs some correction.
Your choice. Some of the most accomplished & famous people in the world have noses that are not considered aesthetically handsome or beautiful. If your nose is hindering you physically or emotionally then you may want to explore the potential benefits of rhinoplasty. Vectra 3d facial imaging is helpful to show what your nose may look like after surgery. Good luck with your studies!