As far as remediation, there aren't many options once the scar tissue has formed. There is a compound, hydroquinone, that is available in a topical formulation which reduces the hyperpigmentation associated with the scars. It is not a panacea, it doesn't work overnight (think 4-6 weeks min. for any noticeable results), and it will make the skin that is treated more sensitive to UV, but if you stick with it, it should lighten even very dark scars to some degree. Caucasians are the best candidates for obvious reasons. It's a legend drug (Rx only) in the U.S., but easy to obtain from a GP or dermatologist. The other treatment is by use of laser radiation to selectively vaporize the melanin and usually the melanocytes by using a tuned wavelength equal to that of the light melanin absorbs (so it doesn't target "brown," but rather the photopeaks of melanin, but that's beyond this discussion). Expensive. Either way, scar tissue will remain.
If it isn't too bad, and it's probably worse in your mind than it is to others, then wear t-shirts that are cut lower, or long sleeves that you pull-up. Really, most people are not doing track mark checks, and even if they are, unless yours are recent--i.e. showing puncture marks, bruising, erythema, redness, etc.--then it's not really any of their concern, unless they are a healthcare professional and should know. Scars show where you've been, not where you are. If all else fails, tell them you were a phlebophiliac and liked drawing your own blood, it isn't completely untrue as you watch for flashback right? Now, if your talking keloid-like monsters on your neck, well you may have to just start owning up...
I have my own tracks man...
NP