I'm a plastic surgeon and get asked about this all the time. The first thing to know is that the scarring you're describing is normal healing. After a brief inflammatory phase, the wound produces a bunch of collagen to form the initial scar. You get exaggerated collagen production, which is why the scar is lumpy. Also, some people just form heavier scar than others. Some people form hypertrophic or keloid scars. There is precious little in the medical literature that is actually proven to work. Scar massage helps to soften the scar and keep it supple and can help flatten the scar if it's persistently raised and lumpy.
Vitamin E oil isn't actually shown to produce any benefit. I know, it sounds like heresy, but it just doesn't shake out in prospective trials. The same goes for Mederma (the few studies are industry sponsored and lousy) but one of my partners recommends it to his patients and he anecdotally says it helps.
If you're really concerned, silicone sheeting is the one thing shown to help. Not a gel or lotion, but a simple sheet of silicone that you can cut to the size of your wound. You have to leave it on as long as possible (at least 10 hours a day, more if possible) for 3-4 months after your laceration happened. You only need one sheet because you can wash the piece of silicone and reapply it. You have to find it online because it's typically not sold in stores. It takes 12-18 months for a scar to mature completely and take on it's final appearance.
And remember, scar tissue will darken at a rate different than the normal skin around it in response to sun exposure, which is why you're supposed to avoid sunlight for a year or so...until it completely matures.
And if all else fails, surgical scar revision is always an option later... Hey, it's job security.
Hope that helps.