I had braces a year ago but now one of my teeth started to move again should i have invisalign or shouldnt i bother thanks?

Retainers: It's not like putting a steel post into concrete. Bone is a living changing tissue. Your Orthodontic Specialist should have made retainers for you to wear after your braces came off to stabilize the result. Return to the Orthodontist for an evaluation.

See Orthodontist: I highly suggest you see your orthodontist for assessment and new retainer. Do not delay.

Up to you: its really up to you. If you want your teeth to be perfectly straight again, you will need some kind of treatment to move them. If you are Ok with where they are now, just make sure to get/wear a retainer to keep them from moving more

Teeth after braces: It is up to you. If you went through expensive treatment once you should probably keep the result at its best. Simple touch up treatment or a new better retainer would help.