Do you think that getting a nose job at 18 is worth it if you broke your nose and it healed a little crookedly?

Individual decision: If the broken and now deformed nose is causing you difficulty with breathing or other functional issues, you should have it repaired if recommended. If it is for aesthetics (looks), then that is a person decision and would be determined by self esteem and personal well-being issues and you and your family and your pcp can discuss this along with any ENT or plastic surgeon you see.

Rhinoplasty Decision: Rhinoplasty is a safe an effective way to alter the appearance of one of the most significant aesthetic landmarks on your face. As with any surgery, there is pain and suffering associated with the recovery process and a financial cost as well. Only you can decide if the benefits of the procedure will outweigh these factors. A surgeon that provides 3d imaging to let you see what to expect can help.

Breathing vs looks: Functional rhinoplasty is performed to correct trouble breathing through the nose. This is usually is due to some anatomic deformity (like a crooked nose). This may be covered by insurance. If you breathe ok, then the issue is cosmetic. If the appearance of the nose doesn't bother you, i wouldn't recommend trying to "fix what's not broken." no hurry, tho, rhinoplasty can be done at any age.

Yes: Both breathing and appearance can be improved with a rhinoplasty.