Lip scar tissue improvement - what options are available? (Photo)

I have an old lip injury from sport (more than 25 years old) which has causes a lip scar on the left of my upper lip. Naturally this mwans that my lips are now assymetrical and a crooked smile. While not particularly bothersome, I've now decided that I would like to improve it. What are the options available? perhaps lip filler to improve the assymetry or a minor surgical procedure? Thank you